How do you rank the different schools of magic?

If Mage Water is #1 for mantle of oceans. Also Blizzard I believe is the best AOE spell.

Fire is pretty powerful.

For me (I usually make Mage sovs)

Water

Fire

Air

Life

Earth

Death

Slow, from Water I, is a curse which provides a benefit similar in strength to the benefit granted by the Haste blessing from Air I, and it costs about the same amount. The only problem it has is that it has to overcome spell resistance whereas Haste will always stick, though it isn't really a problem to overcome spell resistance if you're either high level or have one or two Prodigy traits.

Kill, at Death V, is perhaps the strongest single-target damage spell in the game, though it's a bit mana-intensive, slow to cast, and hard to get (and yes, I know about Mana Blast, but Mana Blast isn't guaranteed to be available in any given game, requires lots of mana to be a guaranteed kill, and costs about as much to cast; besides which, damage beyond the necessary amount to kill the target isn't really worthwhile). Great for taking out one or two powerful units (like Elemental Lords in Wildlands) if your supporting army can deal with everything else while you cast, not that great for dealing with armies.

Pit of Madness, from Death IV, gives you +1 research per essence in the enchanted city and applies the Fear curse to units participating in attacks on the enchanted city. Sadly, it costs you 1 growth, but it's an excellent enchantment for high-essence Conclaves regardless.

Sacrifice, from Death V, allows you to convert half the population of any high-level city you have into mana, at 1 mana per sacrificed citizen. Ever wanted to be able to use the expensive repeatable unit blessings from the other magic schools repeatedly? Ever wanted to make frequent use of spells with excessive mana costs just because? Ever wanted your Mana Blast to deal 10,000 damage per cast? This is one way of getting there, and as a bonus it allows you to make use of a resource (population) which is otherwise useless to you after certain breakpoints (unless you found Blood Curse).

If you're going for a melee Sovereign (or building up a champion with Earth Magic as a melee type), Diamondskin from Earth IV and Giant Form from Earth V are invaluable for allowing you to continue sitting on the front lines even if you don't invest in the defensive traits or are unlucky with weapon and armor finds (or both, to an extent). Earth isn't really a good primary school for a primary spellcaster, however.

Set in Stone, a city enchantment from Earth III, can significantly increase the production capacity of your cities if you're willing to sacrifice the resources and have an essence slot to spare. It's good for a low-essence Fortress pumping out fodder units, or for a very high essence Fortress pumping out elite units. I wouldn't use it on a mid-essence fortress pumping out elite units if I had a training enhancement I could put in the essence slot instead, though I might do it for a mid-essence Fortress pumping out fodder units depending on just what training enhancement enchantments I had available. It also isn't a bad enchantment to consider for hastening the building phase even on research cities, since if you have two or more base materials yield the enchantment is at least as good as Enchanted Hammers.

Regardless, which are best tends to depend on what you want to do:

Create elite units out of Fortresses? Air and Fire, then Earth, then Life; last come Water and Death since they don't do anything for this. (Why is Earth before Life? Because Earth has several spells which provide bonuses to the training of elite units - Aura of Might, Enchanted Hammers, and Set in Stone - while Life only has one, and I'd also rate the Life bonus as the weakest; Air and Fire are ahead of Earth because, even though they only provide one city enchantment each towards making elite units, that city enchantment is really good).

Magic damage? Fire, Water, Death, Air and Earth, Life. Fire before Water because you get to the decent damage spells with less investment in traits, and Fireball and Flamedart are both instant-cast once you have Savant while Blizzard still has a 1-turn casting delay; Water before Death because Blizzard is an army-killer; Death before Air and Earth because of Kill, Drain Life, and Touch of Entropy. Air and Earth are tied in my view more because I'm not really impressed with either school's set of damage spells; Life is last for the rather obvious reason of it not having any damage spells. Additionally, Fire and Water have most of the good strategic damage spells.

Tactical support magic? Air and Water, Life and Death, Earth, Fire.

Strategic support magic? Air and Water and Earth and Death, Life, Fire. Water and Earth have the strategic army stuns; Air has strategic teleportation, army disruption, and emergency army recall; Death has strategic Wither, which as far as I know is not resistible. Air, Earth, and Water additionally have useful unit enchantments, as does Life. Fire doesn't offer much here, unless you consider dropping Pillars of Fire, Starfall, etc on enemy armies until they no longer exist or are nearly dead to be "strategic support".

Summoning magic? Death, then everything else. After all, Death is the only school that still has any summoning spells (Touch of Entropy, which is probably more appropriately called a damage spell, but if it kills something it summons a Lurk).

For me, the ranking goes something like this:

1. Fire/Water
2. Air
3. Death
4. Earth
5. Life

Why is Life last? Because I usually play Empires, and so I don't usually have a good way to get Life Magic. The rest of it is based on me liking to use my champions as tactical damage and tactical support spellcasters, with damage being slightly favored. The top three ranks are nearly tied, while the bottom two are much less used.

Life has an absurdly powerful spell, and it's available right at tier 1: Sovereign's Call. In a game where you win by outgrowing your opponents and the typical maximum growth rate of a city is +3/turn, the ability to add another +2 on top of that is extremely good. It's very terrain-dependent, of course, because without high grain cities you'll have trouble creating enough food to keep up with the ridiculous rate your cities are booming at. Sovereign's Call is probably the main reason Empires can't just steamroll Kingdoms because it gives Kingdoms the strategic advantage of being allowed to just defend - even if the Kingdoms have fewer cities they'll be much better developed so they can still keep up. That forces the Empires to attack the Kingdom players or fall hopelessly behind, and combat extremely favours the defender in this game so that's an uphill battle all the way despite the superior destructive force of the Empire players.

Whereas I'm just the opposite. I tend to play Kingdoms, and use my champions as strategic support and tactical support spellcasters, with defense being slightly favored. As a result, I understandably favor Life/Air for my sovereign, the RNG tends to give me earth for my road-building champion partner. I figure that I can get enough levels in Fire/Water in my subsidiary stack, which not having a dedicated healer is in a support role. And in a pinch, there are spellbooks...

Lightning bolt (Aeromancy?), for high level sovereign, is a very powerful spell. I tend to see it sometimes as a Win button.

- It is very cheap and (lightning) rarely resistive, plus there is no cooldown (yeah!).

- You can cast it in a line of 5, meaning with proper positioning, you can hit 5 units.

Imho this thread shows that the magic is interestingly set, with multiple ways to victory and preferences. No nerfs needed

With so many different uses for spells, it's hard to rank the Schools. I guess that's a good thing.

Let's see, there are tactical damage spells; tactical utility/CC; 'economical' city enchantments; military city enchantments and strategic spells in various forms. I could rank the spell schools in each category and add up the results...although each category's worth is highly dependent on play style and preference. Also, some schools have (virtually) nothing to offer in some categories, while on the other hand some spells are so powerful, they should get bonus points. Oh well, let's rank them anyway. Here goes, from best to worst each time:

Tactical damage: Fire, Water -- Death -- Air, Earth, Life

Tactical CC: Death, Life, Water, Air ---- Earth, Fire

City enchantments (e): Life -- Water, Earth, Death -- Air, Fire

City enchantments (m): Air, Fire -- Earth, Life -- Death, Water

Strategic spells (off/def/cc): Death, Water, Earth -- Fire -- Air, Life

Strategic spells (utility): Water, Air, Earth, Death, Life ---- Fire

 -- means there's a gap between the usefulness of the school(s) on the left and those on the right. I did not name the actual spells, but almost all of them are in the excellent posts above mine.

Conclusions: Fire has great damage spells, but is dead last in several categories. Love it or ignore it, there's no middle ground. Earth has several decent spells, but no game-changers. Life has one spell keeping it alive: Sovereign's Call. Air could have won this competition, if it included all the 'Air-like' spells which aren't part of the school: Tireless March and the Aeromancy spells, for instance. Death and Water are the most versatile spell schools. The only thing they are lacking are the military city enchantments. As I personally never use those, Water and Death are my winners, in that order.

I do actually use slow a lot and I thought I had it in the list, but I guess I overlooked that one not from lack of playing it just simple oversight.

Kill doesn't do a lot for me.  I can see the value of Kill in the main quest and vs wildlands bosses, but I guess I don't play this way because it is too cheesy for me.  I would rather shrink and slow it and then kill it the regular way.  I beat the master quest with Kill once before and I was tremendously underwhelmed.  

One drawback from damage spells is that they force you to play Mage.  Yes, Mage probably is the best type, but it just again greatly reduces your versatility.  Most other schools you can play decently with just Brilliant regardless of what class you choose, but damage magic really wants all its users to be Mages.  Further it wants those mages to invest in +% damage traits rather that investing in other schools of magic.  You really have to pursue damage magic to the exclusion of all else if you want your sovereign to have really amped up damage magic.

If you evaluate schools of magic by how good they are with minimum investment, Fire suffers pretty badly.

If you evaluate schools of magic by how they play in the hands of non-mages, Fire again suffers pretty badly.

Rolling Delin for your wildlands hurts Fire Mages more than any other wildland with any other magic type.  Rolling Quendar as one of your opponents hurts Fire Mages more than any other opponent race hurts any other magic type.

It seems like to me the only way to put Fire anything other than last overall is to seriously underrate what the other schools are capable of doing.

I always choose:

• Earth and Life if playing Kingdom
• Earth and Death if playing Empire

Earth has the enchanted hammers city spell that adds +1 material. This is really important to get your production off to a quick start from your first city. This is better than choosing a site with one more production and one less essence, because the essence can be repurposed later when you have multiple cities.

Earth also has tremor at level 2 that is essential mid to late game for immobilising attackers while your sovereign rushes back from the far side of your empire.

I will only promote beyond level 2 once my mage sovereign has acquired a variety of more beneficial mage promotions.

Life has sovereign's call which is a huge boost to population growth and hence indirectly to production and research.

Some of the later spells are good, but again I will only promote beyond level 1 once my mage sovereign has acquired a variety of more beneficial mage promotions.

By contrast, Death has excellent tactical spells.

Wither may only reduce enemy attacks by 2 but it affects all enemy units and that is a big effect at low levels if fighting a mass of weak creatures and where the margin between attacks and defences are small. It can also be cast on the strategic map just before you attack a stack, to effectively give you a free cast in the first round of combat.

Curse only affects one target but entirely negates it's armour. Great for strong monsters or for plate clad enemies later in the game.

At level 4, mass curse makes a battle changing difference against those plate clad stacks.

Fireball is a great damage inflicting spell but you can get it via anointed with fire without ever taking the fire school.

One of the best mass combat spells of all is pull of the earth which causes enemies in an area to lose their next turn. But again, this is not from a spell school, but rather a promotion on the mage path.

My sovereign will take the mage class with prodigy(?) route to reduce spell resistance until the promotion that reduces combat casting times by 1, picking up pull of the earth on the way. Now he can cast fireball or pull of the earth every round, without ever investing in the spell schools.

In short: Air (2nd level) to begin with. Tutelage is THE spell to level up your heroes more quickly.

BTW I just love the AI tweaks of 1.4 !

In the Beta, you could research Pull of the Earth, and once you had it, all your Champs could cast it!

I highlighted the incredible awesomeness of this spell in a couple of posts back then. At some point, the Devs ninja-nerfed it. I believe those two events are connected, but I have no proof 

Back on topic: I always hope for an early champ to grant me some Earth magic, as Enchanted Hammers, Tremor and the unit enchantments are all lvl 1 or 2, and it doesn't really matter who casts them. In that sense, there's a slight difference between 'ranking the spell schools' and 'best spell school to select/have for your Sovereign'. It's funny that you are very much aware of that last concept - your Fireball strategy proves as much - and still make different choices than me 

1. Water - Blizzard, mantle of oceans, Vet's Howl

2. Fire -  Firestorm, fireball, flame dart

3. Air - lightning spells, evade

4. Life - Heal, well spring, cloud walk, shrink, growth

5. Earth -  move earth, summon beast

6. Death - blind, death - otherwise "meh"

Are you kidding me?? You missed out Curse, Mass Curse, Wither and Sacrifice. At the start of the game Wither can win you battles that you couldn't win otherwise. If cast strategically it's more expensive but cannot be resisted, it can be cast outside of your territory and has a short cooldown. This makes early monsters a walk in the park, especially on higher difficulty levels where they generally get more hitpoints but not higher attack.

Curse is better than Blind for high armour units. Mass Curse is a highly effective way of killing ludicrous armour AI armies. Get to Sacrifice and your mana worries are basically over, even if you want to cast some of the higher cost spells. Whether deliberately or not this has been nerfed somewhat by reducing the population you get when you conquer cities. I don't think this used to happen; I've gained hundreds of mana when conquering AI cities on high difficulty levels; if it did happen I didn't notice before 1.3 or 1.4. The 1.5 patch notes state that the reduction in population is going  up to 75% of the conquered city. This reduces the power of Sacrifice, however it's still possible to gain substantial amounts of mana by farming cities for Sacrifice population in the same way you farm them for pioneers. A Town with Festival is good for this (+6 growth per turn).

Kill may feel a bit unsatisfying but will kill anything if you cast Shadowbolt enough times on it to soften it up first. It makes Elemental Lords and the Quest Victory very straightforward, and can help in Dragon fights. Personally I always find the Quest victory unsatisfying, I rarely lose a unit, so it doesn't make much difference if I use Kill.

In terms of which is strongest, it does depend enormously on your playing style, but personally I would go with Water; Freeze is an extremely helpful spell, as is Slow, Mantle of Oceans is a gamechanger in terms of easing your mana worries, and Blizzard is an army killer. I also like Air, although it takes till level four to get the really good stuff, i.e. Titan's Breath and Cloudwalk, level five before you get Tornado. I've detailed in anther of my posts how Titan's Breath with -1 turn casting time can be used to stop all prone vulnerable units from ever having a turn; it was part of my strategy to beat the AI on Insane. I prefer the Death factions, but I'm currently playing as Tarth with Life magic and I agree Sovereign's Call is very powerful. Heal can be very effective in the early/ mid game, if you have the mana, and Wellspring is a great spell. Life also has a couple of decent late spells, Call to Arms is very handy, and Crusade is not bad. Death Ward is ok, although I don't normally expect to be losing units anyway. 

Earth has handy spells, Tremor and Nature's Cloak and Enchanted Hammers are all great low-level spells. Nature's Cloak is more or less a requirement before tackling Drakes or Dragons. Lower Land and Raise Land may be helpful in particular circumstances. I'm not that bothered about the later spells; if I can get a hero to level 2 Earth that's probably fine.

The one I'm unconvinced about is Fire. It has ok damage causing spells, but they're quite expensive, and a lot of units get fire resistance. Fireball is not as good an army killer as Blizzard, and as Justamo pointed out you can get Fireball even if you don't have Fire. Heart of Fire is good but is quite expensive in mana and can be duplicated by amulets etc. (assuming you have the crystal). The later Fire spells personally strike me as a bit rubbish, but again this may reflect my playing style.

So in answer to the original question, I'd rank them something like:

Water; Death; Air; Life; Earth; Fire.

The first four are fairly close for me; Earth is handy to have for the low level spells. I'm generally happy to get a hero with any of the schools I don't already have, if only for the strategic spells. The only one I can't get excited about is Fire; if damage spells are your thing then great, but personally I lose interest after Heart of Fire. But this does depend enormously on your playing style.

 can't really rank death magic since i rarely play empires. my ranking for the other schools:

1. Life - no contest. healing spells are just too good, and shrink is a very potent debuff (possibly the best debuff in the game, except for a  heavily water shard buffed slow). sov's call is probably the single best city enchant (IMO) and regeneration is one of the most powerful unit buffs (full heal between seasons) call to arms, crusade and deathward are just icing on the cake (if you have too much mana in the end game)

2. Water. Slow is awesome, pandemonium is probably the most undervalued AoE spell (no cast time if you champ has the Savant trait; it's a bit chaotic which makes it unreliable, but both the daze and slow results are very useful; the damage result is fairly useless though); mantle of oceans is great, blizzard is a really deadly spell vs. multi figure units (unlike fireball, blizzard deals damage per figure, which can be rather crazy vs. 6 figure companies); freeze is probably the best strategic spell throughout the game (tied with Earth II tremor - good synergy if you have both). tidal wave and vetrars howl can be very deadly on the strategic layer.

3. Air. tutelage for heroes, haste for early game, aura of grace probably the strongest fortress troop enchantment; titans breath is really nice for tactical (AoE knockback/knockdown); windwalk is a great strategic mobility spell. tornado is still a very good strategic spell (used to be my favorite strategic spell when it was cheaper; now at 150 mana it's still worth using sometimes). if i have way too much mana, the repeatable +1 init spell is also fun to create a superhero.

4. Earth. tremor, nature's grace (? not sure about the name - the troop buff that gives elemental resistance) and hammers are very useful; set in stone is good for quickly building stuff in newly founded cities; earthquake can be devastating, though too expensive to really spam it (most of the time); giantform and diamondskin can turn a high level warrior or assassin hero  into a truly unstoppable wreckingball. 

5. Fire. it's great for damage spellcasters, but i rarely use those (prefer defenders or warriors backed up by healer/supporter mages/commanders). the fire aura for troops is very good (IMO it's the second best after the +init buff -if i want to play with elite troops, those two are mandatory) you only need fire 1 for the buff, though - if you don't use a damage spellcaster champ, there's little reason to go beyond fire 1. maybe fire 2 for the +fire damage buff for heroes if you have lots of fire shards. fireball is pretty strong on a specialized fire caster. with all the evorker traits and savent, you can burn down full armies before they even get close.

Yea the curse spells are useful, but wither is underpowered unless you can get your hands on a bunch of death shards. And personally I never saw the advantage of sacrafice over other options. I'd rather have the unit alive and continue fighting. If the sovereign dies, all it costs is some manna.

Sacrifice doesn't do anything at all to units. You might be thinking of Cull the Weak (kills a regular unit to heal 20 health on the caster and generate 20 mana) or Infernal Covenant (permanently kills a champion to summon a [champion's level + 7]th level Death Demon who sticks around for the duration of the battle). Sacrifice converts half of the population of one of your cities into mana at a 1:1 ratio. Since there are points in city development where the population really doesn't matter, this is more or less a source of free mana (and using it on level 5 cities has little real cost associated with it, unless you really wanted to use that city for churning out Pioneers). The only three things that Sacrifice really competes with are Blood Curse (sacrifice city population to increase the caster's health), city growth (which doesn't matter if you're casting it on a city which has no reasonable prospect of reaching the next level in a reasonable time period or which is already level 5), and Pioneer training (but since you're probably targeting a high-population city, and probably aren't doing this terribly frequently, shouldn't cause too much difficulty).

As far as why Fire is attractive - it's a minimal investment tactical damage magic school. Everything you need is available in the first three ranks, and you can pick up the first two on sovereign creation if you wanted to have it; Fire III is available by level 5, and unlike Anointed by Fire requires neither a 1-mana-per-turn upkeep nor any specific research path. Even though Fire Resistance and Fire Immunity tends to be more common than other elemental resistances and immunities, it isn't common enough in most circumstances that Fire damage isn't worth having. If you're not interested in playing tactical damage spellcasters, then Fire isn't for you. If you are, then it's your go-to choice for a minimum investment damage school. Fireball isn't the army killer that Blizzard is, but it's faster to cast and easier to get, which makes it more likely that it won't be counterspelled (and it can be made impossible to counterspell with Savant, unlike Blizzard). The fourth and fifth ranks aren't that attractive, but they also don't really need to be if what you're looking for is a minimum-investment damage school, since Flame Dart and Fireball are good spells available very early on (though they probably won't be worth casting except in extremis until at least the later part of the early game, due to mana issues).

I would argue that Fire isn't really a minimum investment damage school.

Slow is maximally effective when you have it and maybe one or two levels of the traits that reduce resists (Prodigy?).

That is a 2 - 3 trait investment.

Fireball is 3 traits itself, it wants all the resist reducers and the -1 cast time AND it wants +20% damage traits as well if you want to use it at maximal effectiveness.

Air is even lighter weight in that Haste is maximally utilized with just 1 level in Air and nothing supporting it.

I have casted a lot of Fireballs through Annointed by Fire without any of the +20% damage abilities (and without being a Mage at all) and I have generally been underwhelmed with the damage.  I have had it kill quite a few low HP things, but most of the stuff I really care about is still standing afterwards.

Fireball has its uses. Killing ranged units before they can damage or kill your heroes or ranged units springs to mind. Its particularly good against Shrills or Darkling Shamen for this, I've used it to clear everything except the boss from a Wildlands before,  meaning I could pick up all the goodie huts fairly early in the game. Causing damage to very high armour units if you don't have Curse is also a reasonable use. However it's quite expensive, and Blizzard wins hands-down as an AI army killer.

Having Blizzard countered is annoying, but I've only had the AI counter me a few times; if you have a spellcaster with high enough initiative then you may be able to time it in the initiative list to go off before the enemy spellcaster gets a turn. Interestingly Command does not work. Your spellcaster immediately gets an extra turn to do something else, but the spell itself keeps its previous position. However in practice being countered is rarely a problem if you have a high enough initiative; Haste on you and Slow on the enemy spellcaster obviously help. Sometimes you can also wait for the enemy spellcaster to start casting a multi-turn spell of their own.

Incidentally has anyone else noticed enemy spellcasters casting more spells since 1.4? In my last battle once or twice I thought the enemy hero should actually have waded in and done some damage rather than casting yet more buffs and debuffs, but in general this part does seem to have improved a lot. High level enemy spellcasters will now do something other than cast Burning Blade and hit you with their sword.

How about this for a combo: get Water magic from an early Hero (Steal Spirit) or Pariden, use Empire and choose Death II for Sov and Death Worship for Faction (I also used Undead, Gravetouched and Rebels).

I've having an epic game of 1 Undead Conclave town with outposts against the world - my Sov and Bacco and 5 ghost units with Maces and 24 armor and as as many initiative boosting items/effects as possible (try Amulet of Haste, and Amulet of Haste II or III from Primal Savage's XtraTrading mod, and Aura of Grace).   Funny thing is Undead with Rations...

How about a 1 turn Infection (Mage Savant), combined with Graveseal, Slow, Blindness, Curse and Wither - no armor low attack inaccurate enemies that always receive crits - joy!   I have been using Bacco from my NoXPSplit mod, he can sometimes cast Infection before I get to Savant with my Mage Sov.

You're ignoring my point. If you're interested in playing a tactical DAMAGE mage, then you're going to be picking up the Evoker traits and Savant anyways, and Fire II and III are at most a two-level investment (or a 1-level investment if you started with Fire II). And unlike Anointed by Fire, having Fire III on a champion doesn't require 1 mana per turn, which depending on shard distribution and essence availability can potentially be a concern into the later stages of the mid game, and possibly even the end game (yes, you'd have to be really unlucky, but then again I've played on a huge map where only three of my 14 cities had any essence at all because there just weren't that many essence locations to start with, and most of the remaining available land also didn't have any available essence yields).

Neither Haste nor Slow is a damage spell; Blizzard requires a minimum of two levels invested into Water Magic and isn't a versatile spell unless you consider a big hammer of army-smiting as the solution to all your problems, and is additionally worse than Fireball if we're targeting single-figure units or enemies with a decent chance of successfully casting Counterspell. Chaos and Pandemonium, the other spells from Water Magic that can deal damage, are unreliable damage spells because they aren't guaranteed to deal damage and moreover the damage that they deal isn't particularly good (this doesn't make them bad support spells; as Azunai_ said, the Daze and Stun effects that these can apply are rather useful, but these aren't good damage spells). Air Magic tactical damage spells aren't that good - Storm hits a random enemy, and Thunderstrike puts the caster in melee range if you want it to deal any damage - so Air Magic isn't something to turn to as a damage mage, and it additionally requires a minimum of 1 level invested in it to have any damage spells, with a required minimum level of 5, because the first damage spell in Air is available at Air III. For the same amount of investment in Fire, you've already gotten three damage spells - Burning Hands (which has all the problems of Thunderstrike for a primary spellcaster, but is available much sooner and is nearly four times less expensive to cast; at 10 mana per cast and dealing 10 fire damage to up to three adjacent targets, it's additionally possibly worth casting in the early part of the game), Flame Dart (which isn't worth casting early because its primary damage is a multiple of your level and it costs twice as much as Burning Hands to cast), and Fireball (which, though a little too expensive to rely on in the early game, can be used to shift the balance of power in one or maybe two early battles, or as a last resort if you run into a fight you can't handle with just your regular army).

Earth Magic tactical damage spells are quite bad - Shockwave deals less only 55% of the damage that Fireball does (though at no casting time regardless of Savant), requires your caster to be in melee range of all of the targets (who are ideally surrounding the caster - if you think this is an acceptable position for a primary spellcaster, I think you need to reevaluate your tactics), and costs 20% more mana to cast than Fireball does, while Fracture deals damage equal to 25% of the current health of the target and weakens its physical defenses, but can be resisted to completely negate its effects, and has the same casting time as Fireball does - so it's not a primary school for a damage mage, though it could be useful as a secondary school (but still, not for the damage). Additionally, as with Air, Earth Magic damage spells require a minimum of 1 level invested into Earth Magic.

Death Magic damage spells are all single-target effects, now that Contagion is gone, so it's not a very versatile damage school. Not bad as a secondary school for a damage mage, though all of the good damage spells require at least 1 level invested because they are all at Death III or higher (and no, Shadowbolt is not a good damage spell; it's not resistible, but the damage is pitiful and it costs only 6 mana less than a Flame Dart before accounting for the Mage discount; the primary use of Shadowbolt is for reducing spell resistance, not dealing damage).

Life doesn't have any damage spells at all; need I point out how useless that is as a primary school for a damage mage? It's fine as a utility school, but it doesn't really offer anything to a damage mage unless you're fighting a magic-immune target or you only have one available type of elemental damage (you shouldn't, in case that wasn't obvious).

Fire/Water, Fire/Death, and Death/Water are great combinations for damage mages, as they combine a decent mix of AOE and single-target damage spells; additionally, Fire/Water and Fire/Death are slightly superior to Death/Water as Fire needs very little investment in order to gain access to its best damage spells. Since I like to play with tactical damage spellcasters and tactical support spellcasters, I rate the schools with good spells for those types highly - namely, Fire, Water, Air, and Death. I only rated Life so low because, since I usually play with Empires, Life is rarely available enough to be useful to me - it doesn't matter how powerful the school of magic is, if I can't use it it isn't going to rate highly in my ranking of the magic schools; if I usually played Kingdoms rather than Empires, then Death would occupy the position Life does now. Earth ranks just above Life because it's available to me, but it isn't really designed as a primary spellcaster's main school of magic, and since I like my champions to be primary spellcasters, it's mostly fine for me if I have even just one champion in my entire empire that has it, nor am I particularly disappointed by not having it available.

Your argument is that Fire Magic isn't as good a magic school as Air or Water because it doesn't have utility spells like Haste and Slow, which are admittedly powerful, useful spells (and a large part of why Air and Water rank in at #2 and #1 in my listing), but it doesn't speak to the reason why I ranked Fire at #1, that reason being damage. No other school of magic provides as versatile a set of damage spells as Fire does at as little investment, nor is Anointed by Fire completely superior to taking Fire III (for one thing, maintaining that enchantment on a single champion costs as much as one Fireball every 38 turns; for another, it requires you to research Rituals, which isn't a very appealing research line if I don't have a decent source of crystal readily available). Water Magic's only real damage spell is essentially a blunt hammer that works really well on large armies of multi-figure units, but isn't so useful against single-figure units and isn't necessary against small armies. Air Magic's damage spells are either unreliable or put the caster into a bad situation if you want to use the damage, while Earth Magic's damage spells are weak and expensive. Death Magic damage is all single-target, and the good damage spells come no earlier in the tree than Fireball (incidentally, if all you care about is damage and not the mana required to deal it, Fireball is a better single-target damage spell than Drain Life is, and is nearly as good as Touch of Entropy assuming no shard bonuses on either side, though it's much more expensive to cast). Fire gives a flexible set of spells quickly. What more could a damage mage ask of a single school of magic, except for untyped damage on those spells?

If you only ever play mages and the only thing you ever want them to do is deal direct damage to enemy units, then I guess Fire might as well be the number 1 school.

I just think a school of magic needs more than that in order to get out of last place overall.  

If you are last on every list except one and first in the exception list, you are still last overall.

A better question in regards to Annointed By Fire is what you gain and lose by using it.  If all that matters is getting Fireball, the difference is between using a minimum of 2 trait picks and a minimum of one level and one more of either vs maybe 200 mana spread out over the whole game.

If I could pay 200 mana over a whole game and buy myself 3 more trait picks and 1 more level (or 2 and 2), I would pay that.

If only that was considered, ABF would be strictly superior to the whole Fire school.  However, that isn't the only concern.  ABF doesn't give all the other spells in the school.

The question then becomes what percent of the entire Fire school of magic is tied up in Fireball?  I would argue that it is upwards of 90%.

In the Toolbox of Fire you basically have a screwdriver, a hammer, a slightly bigger hammer, and a slightly bigger than that hammer.  For some problems it helps to have a hammer of size A instead of a hammer of size B, but for some problems it helps to have a wrench, a saw, or a pencil.  A hammer isn't remotely like any of those things.  

You can try to use a hammer when you really need to be using a wrench, but it's far from optimal.  The crux of Fire's problem as a school of magic is that there are only so many problems that can be solved with hammers.  At some point it is better to have a wide variety of tools rather than a bunch of different sizes of the same tool.

What I read from you is all true. But that doesn't really help. Why? I want to answer this by sharing my experience with you.

I now play the second highest difficulty level (I don't know the name in english). I tried several strategies and lost.

Now I try to boost research, population growth and production. The goal is to get an army of mages as soon as possible. To win a battle it is important that your troops can act first (that means they need a high initiative).

- Thus I alwalys take a leader as sovereign. He can greatly raise the initiative of your troops.

- I want my cities reach as soon as possible higher levels. Thus LIFE and EARTH are my favorite magic schools. (A level 4 conclave gives an additional essence and a +2 crystal income.)

If I have luck I get a hero with AIR magic. 25 % experience for my sovereign and up to +5 to initiative for my troops is awesome. AIR is the strongest magic school but as I wrote you first need to be able to produce troops. Then you can bring the focus to strengthen your army.

Until now this is the best way to win at high difficulty level. Let's have an eye to my strategy: If you assume that your enemy traces the same strategy (procucing troops with high initiative) and if you also assume that he has the same requirements (= for example same equipement) as you you will ALWAYS beat his army if you have a leader as sovereign. Why? Because a leader boosts the initiative of your troops. The enemy might have a very strong mage or fighter but his hero will never be able to cast a spell or attack something. If all your troops have a higher iniative then the enemy troops your mages (or archers) will easily be able to kill the enemy hero in the first round. He has no chance to survive and will never be able to do something. If you play with the tarth race this strategy becomes even stronger: Two attacks in the first round greatly decimates the enemy army. In addition to the death enemy hero you will be able to weaken the enemy army so much that the surviving enemy troops are no danger.

PS: My native language is German but I assume you understand me. 

Actually it does help.  It is just for those sort of reasons that I rated Air as the strongest type of magic in the OP.

I put Life second also for the same sort of reasons, Call to Arms is quite good if you have spare mana around and Sovereign's Call is as powerful as two towers with Consulates.  Shrink is maybe the best debuff in FE and that is also a Life spell.  Heal and group heal are also pretty good.

I rated earth much lower, but I still very much like to see that in my games as well.

I also pick Commander for my sovereign and focus on the lower track with it to get the extra initiative, experience, and to never miss.

Your strategy isn't far off from what I do in a lot of games.

I would never use Tarth, though.  Armies of size 3 are just too small.  Even size 4 is too small.  I guess it would be good not to be attacked by monsters and to be able to expand quickly, but I would rather use the same abilities with some other blood if it came down to it.  Tarth blood is just not very good.

Phew, I am glad there's some discussion about Fire. Because all the consensus in this thread is making my head spin.

Come on people, this is a forum on the Internets! Where's all the flaming and trolling? Geez 

Maybe it's because of the solar eclipse. ;-)  Making everybody (at least most people) nice.  Stranger things have happened.

Who said that I only use 3 troops in my army??? The Tarth race is still the strongest one due to the double attack.