How will 17% air magic resistance counter “teleport enemy” spell? In the same way as 17% general magic resistance – it just wont.
It could always reduce the maximum teleportation distance. Resistances can reduce the effectiveness of spells. If a spell does damage, resistance would reduce the damage done. If a spell slows, resistance would reduce how much the target is slowed. If a spell does something like teleport, the range would be reduced. If a spell does something binary, but with a duration, resistances could reduce the duration... I think you'll find that most spells actually fall somewhere within these categories...
And that's one of the reasons why it's complex.
No, there is not any logic to it because as you said, it's arbitrary and subjective.
So you're saying that there is no logic behind a lava-dwelling salamander being highly resistant to fire-based damage and effects? Sure, someone could create a perfectly self-consist magic system in which lava-dwelling salamanders are hurt by a fireball just as badly as, say, an Ent. But it would be confusing, because it contradicts our reality-based preconceptions.
In fact I would argue that in most cases, resistances are indeed pretty straightforward. A creature whose natural habitat is, say, extraordinarily hot should be resistant to heat (fire)-based damage and effects. A creature that is made of flammable material should be vulnerable to fire-based damage and effects. And so on. A creature that bores through rock shouldn't have to worry much about being buried underground by Earth magic - not only is that its natural habitat, but it can always just bore its way right back out again...
The matter is complicated when talking about elementals because while a fire/earth/air/water elemental might live in fire/earth/air/water, they are also made of it. And so while they should be resistant/immune to the relevant damage type, a magic-user whose specialty is control fire/earth/air/water should still be very effective at countering them. For example, there could be a "snuff flames" spell in the fire element that, instead of inducing fire damage simply puts out fires. It could be used to disperse an opponent's fire wall, or fiery weapons enchantment, or even a fire elemental... This is an example of the complimentary nature of magic resistance types and disparate magical schools/elements; the combination allows, in this example, a fire elemental to be resistant/immune to fire damage, but not to every fire spell.
Of course this is what makes sense to me, and being as we're talking about magic here anybody is free to make up their own magical rules. Personally I prefer mine to be logical abstractions and extensions of reality than wacky contrivances with no connection to reality. In the latter case, the magic system would be complex. In the former, not so much. If I was reading a description of a Fire Salamander and all of a sudden noticed "Weak to fire, strong against water" I would be like "What the @#$&? Where did that come from?!" - and if all such resistances were in the same vein I would never remember any of it. On the other hand if I saw "Resistant to fire, strong against water" I'd think, "Ok, I can see that," and I would probably remember it from then on, because it is intuitive.
Then if Fire Resistance is useless against Flare, does that mean we need yet another Resistance stat for this? If so, how it combines with Fire Resistance? Or does that it mean Flare is unresistable?
I suppose it depends. The best way to handle things like that is probably ala HoMM. 'Immune to mind spells' and 'Eyeless' come to mind; creatures with these traits would be immune to mind spells or blind, regardless of what spell from which element was used. Unless, of course, you want to be able to blind eyeless troglodytes, or hypnotize mindless golems.
Just to clarify, I wrote "...very little EXTRA tactical decisions..." (emphasis on extra).
Then your wording was unclear: "It offers very little extra strategical and even fewer extra tactical decisions compared to general resistance." I suppose that could be taken either way. Nonetheless I entirely disagree with your assessment that the only thing it adds is the obvious decision not to use fire magic against fire immune creatures. See my previous posts...
Problem is that attacker has to pick "first" and you might try to balance between those two extreme cases, but you have to do a compromise which will either favour resistances or magical studies. The more types of magic you have, the bigger the problem is. Lets not forget that we can design our units so min-maxing will happen. Lot of games avoid that by having prefactored units.
Why do people always ignore my previous posts when responding to a later one? The result is a discussion that just goes round and round in circles. Like I said SO MANY TIMES, in my opinion resistances for regular, trainable units should be more of a convenience than a major component of strategy. Honestly I don't really care all that much of resistances for regular units are even in the game - I'd like it if they are but I wouldn't particularly mind if they aren't. You cannot, however, design your own dragon, or ent, or elemental, or kraken - they are what they are and they have what they have. No min-maxing to be done and no 'picking' to be done.
On the other hand if you have just magic (of any kind) vs anti-magic system (that is one universal resistance) than you can make research of both somehow equal (obviously with some nonlinear scaling). So you can have "stupid" barbarians that are immune to your smoke and mirrors, but they have in fact invested as much resources as you had to achieve that. Plus they almost surely wont be "completly" immune as that is kinda privelage of a few. While balanced, this system preserves uniqueness of magic types (as long as the spells differs more than just in colour), because you can still choose which type of magic suits you more (or which node is closer...)
I'm fine with the ability to focus your magic research in such a way that allows you to impart magical anti-magic properties to your units. That could be a fun way to play the game now and then, and could even be combined with the 'regular' aspects of magic to create something of a middle-ground.
Regarding the bold section: no it does not preserve the uniqueness of magic types. It is the exact same thing as a system without magic damage/effects and related resistances, with the ability to specialize in a typical 'barbarian mentality' (which I think was already ruled out by the devs). Nonetheless in that system I still cannot have lava-dwelling salamanders that are resistant to fire and weak to water, and so on...
But truth is, that creating elemental immune just to fire would have to be done in some other manner (tags just for these special cases?).
Whether implemented as tags/traits/properties/abilities or as resistances stats in line with ATK and DEF is irrelevant. The same effect is achieved, and neither is really any more complicated than the other. Really, tags are slightly more complicated than stats, with the added benefits of being more versatile and visually cleaner. If you think stats would result in an unbalanced system but tags would not, then you are confused because they are in effect pretty much identical.
But this is sarifice I am willing to make to have actually balanced system, which is immensly important in multiplayer game.
Elemental is not a multiplayer game. It is a single-player game with multiplayer functionality... Or at least that was the original intention. Brad has stated that he will not dumb down or remove features that are great in single-player just for the sake of multi-player. Don't expect Stardock to be tweaking Elemental every few months for the sake of multiplayer balance like it's Starcraft or a competitive RTS.