As pure combat machines, yes, they do suck. Excepting the Marza which is a special case, and maybe a few others. A single cap against 5 HC's is pretty dicey for the cap.

But as aids to your fleet for specific abilities, nothing touches them. A couple of Kol's will clear the skies of strike craft. Dunovs can regen your shields/anti-matter. Akkans can boost the range of your LRF's and give you a pretty survivable front line colonizer. Not to mention the Advent Holy Trinity, and some nice Vasari tricks.

Think of it this way: 500 fleet points, me with ONE cap. If I have something that gives me a 10 percent boost to range like the Akkan ability, I get to shoot first. Assuming we both have all kodiaks to make this simple, that means I get to inflict ( 45 kodiaks versus your 50 ) 45 x 20 points ( 900 ), assume upgrades for easy math, before you can fire. By the time you get to fire, I fire again as well, and you lose your first ship. Go after the Akkan, and by the time you kill it, you'll have lost another 2 or three kodiaks. Now it's about even. Enough to turn the tide ? Maybe. But it's a simple example ignoring mitigation and tactics ( like kiting my akkan, and chewing up your kodiaks from behind with my own where you can't return fire ). Swap the Akkan for a Dunov, and it can restore 700+ points of shield at a shot. Thats almost the output of your entire fleet, in effect nerfing your damage for several exchanges. Other examples get more complicated, adding Hoshikos, LRM's, and light carriers. What about an Advent cap dominating ( stealing ) a few of your ships ? Just three would make it a 48 HC's + cap versus your 47 HC's...  

Caps give your entire fleet a 'little' edge. Buying a cap to give a 10% boost to the damage of 5 cobalts is stupid. But 10% to 30 kodiaks ? Or 100 cobalts ? Well, hey, thats worth looking at.

Caps are like frosting. Great, and everyone loves them. But kind of silly without the cake ( the rest of your fleet ).

Also it's never fun to have your ships eaten by the Egg. With focus fire -6 armour it's incredible, and the damage goes straight to the hull. Also Advent shenanigans with their abilities make the game easy for a clever player. Imagine:

Radiance Battleship- Animosity (sucks in all enemy fire)

Rapture Battlecruiser- Vengeance (enemy damage to said Radiance is reflected)

Progenitor Mothership-Malice (reflected damage is multiplied) + Shield Restore (Radiance does not die)

All the enemy attacks now get thrown back with interest, not even counting your own fleet shooting them

Also a Halcyon Carrier gives you a fire rate increase for all ships, so they do as much damage as 15% extra ships (and the strikecraft it has are pretty useful too)

Akkan can stop everything with it's ulti, that's the kind of divinities that you can't touch with 50+ HC. 

And thats why I play Single player alot. I make fleets of Caps and thats it!!!

I also do that, you can easily win withnothing but a fleet of 8-12 cap ships and just a few supporting ships.

If you are playing vs the AI, try the mod = Real Capital Ships V1.11, makes the capital ships as they should be - truely epic !!!  great mod !!

I play as vasari and you know vasar caps YUCK! not the best out there. Advent caps are by far the most needed for a fleet of their own kind. But have you seen the vasari egg take out ships.

Example i had the egg and 10 skirmishers (very early game for me probally 3rd or so) The enemy TEC had 25 cobalts. Now even though skirmishers are better he still had at least 60+ support in frigates. Now a level 3 egg with it's nano disassembler can hit a frigate. Let it die to the damage while attacking another with the frigates. Fire another. BAM BAM BAM. I didn' twin the battle, i lost all 10 skimrisher but the cap stayed alive and even though he phased in anotehr 5 LRM's he was left wiht only 10 ships when i had to run. I ran the cap ship to my nearby planet to a repair station and watched it repair. Got 10 assaliants. (now it's level 5 or so can't remember) I warp in 25 cobalts or so vs my now level 5 cap. They couldn't damage it fast enough. I got smart and let the cap draw the fire and assaliants kill the cobalts. Won wihtout a loss. Caps do suck.

Desolators as said above are great ships. Assaliants on steriods. Truth is as vasari i normally only get one to 2 caps. But the initial boost is so great. Try a game without cap ships. See how far you get. Fight someone who uses a cap in his fleet. ONE is enough to change a battle. Plus being very usefull ships. The EGG's planet drain does 45x30seconds damage to a planet plus gives you 15x30 of every resource. So now you get 450 crystal 450 metal and did tremendous damage to a planet. Use it again. JUST PAID THE CAP OFF.

I've done a little playing as TEC and Advent. Marza is awesome. Had one marza the ai had a Dunnov and 3 frigates. He had more support. I took out the dunnov and the frigates ran. I won. Advent i had 10 disiples and a progenator level 3, enemy was vasari he had 8 skirmishers and kortul. Despite his obvious advantage i was able to do significant damage before i had to run due ot the progenator pretty much tanking almost all damage thrown at it. Took the skimrishers out around it then had to run my cap. The discples too. Didn't lose more than 3 ships. He lost all the skirmishers.

They give you those little boosts if used correctly that even fleet sizes become quite a bit better than something of even support. Caps get good around level 4 get them their fast and they don't really suck.

Ok, for the record, level 1 cap ships suck.  However, as it level's up, they quickly become worth their weight and are a much better value than an equivalent number of cruisers/frigates.  If someone kills your cap, you don't have to do the research again, just buy a new one.  If you have 3 or 4 caps running around, it shouldn't take you more than 2-3 minutes to get enough resources to buy another one, because at that point you should have some type of econ up.

Agent of karma- What are you talking about. A several hour long game. But have you played a 40 planet random online. You may have 6 planets and that resource boost gives you several decent ships plus great bombarding along with it's nanodissassemlber. I haven't had a game that if the space egg hit level 6 that it didn't pay itself off almost the first time i used that ability.

Your point is, you won, and the space whale helped you win.  Understood.  However, as cool as the space whale is, was it worth the 3000 credits + metal + crystal, plus 50 fleet cap, plus the money to buy another crew for it, plus the factory to build it, etc?  In other words, if you had put all of that money into assailants or something, would you have gotten a better bang for your buck?  It seems you would have.

Really i'm not sure on that. Level 3 space egg. Hit it with nano dissassembler boom one dead in 15 or so sseconds. Meanwhile you damage another halfway down. Boom hit another wiht dissassembler. You kill the other one. For 7 1/2 assaliants for the cost of one space egg. Within maybe 35 seconds half of the fleet is gone. Half of a fleet is half it's dps while half of a cap ship is still half of a cap ship same dps and even more hull due to mitigation. Theres many ways they become usefull. Marauder's are great. If you get them to level 6 you can use them as a phase stabilizer node. It's easier to get a single ship in thier back worlds then sending a 10 bar fleet. Sure a level 1 space egg is dead but level 3 or level 4 gives even better abilities.

Plus to get the same abilities as the colinizing cap you're buying a colony ship too so you're at 6 assaliants to one cap. The cap can also bombard. To bombard you'd need to take off another 2 assaliants so you're down to 4 assaliants 2 devastators and a colony ship. To get the nano dissassembler ability or something of the same worthwhile you'd need maybe 3 enforcers. Plus whatever you get in strike craft so bam. Who wins there. Capitals are versatile. They are meant to fill roles that a less balanced fleet or less researched fleet lack. Lets say you don't want to get enforcers but you still want DPS get the kortul.

P.S. sorry for all the vasari based answer's they are practically all i play. Plus the egg is a great example. Vasari capitals focus more on one ship as a super versitile weapon that specializes a little more in one thing. Advent need a mix and tec don't really need caps to a huge extent but a marza and kol do help.

It is true that capitals ships are weak on firepower for their cost, with the exception of some super abilities.  Early game, if someone spams level 1 capitals, you chase them down and kill them like dogs with your LRM / Bombers.  

The power of capitals is they add strategic and tactical abilities to your fleet you can not otherwise get.  Capitals also contain some counters that have a tremendous amplification effect on the effectiveness of your main battle fleet, essentially making up for their cost.  Small fleets often don't have the firepower to justify some of these abilities, but bigger fleets do.  If you are winning already by this time, it just means you didn't need a 2nd cap, but trust me, you can actually turn a game around with the use of powers on a capital.  Some of the nastiest end game fleets are build around strategies using multiple capital ships along with the support cruisers / repair to keep the capitals up and safe.

Evacuator (Egg) is not really a good fleet mesh ship. But it can rapidly suck down an unfortified world and colonize it giving Big Strategic benefits in Multiplay.  It does well in smaller engagements because it can eat ships and make them vulnerable to fire, as well as STOP THEM FROM PHASE JUMPING and escaping!  It may not have been worthwhile to you in your game because you are winning, but in a close fight, it is crippling to have one of these running around assassinating worlds.

Kortul   - Explosive Nanites can start a chain reaction of destruction on a fleet... can be kind of hard to pull off, but very rewarding if you do.  Otherwise, relatively hard to kill and good at killing other capitals and offering some anti fighter protection.

Marauder - Phase out Hull for saving friendly ships from destruction or singling out enemy ships from the enemy fleet so they get seperated.  Level 6 ability for strategically allowing a fleet to warp in from your phase gates.

Skirantra Carrier - AoE Healing!   Micro-Phasing Aura makes your own fighters hard to kill.  BTW, stick 3 of these in the middle of a big ass fleet of Vasari, along with some overseers to keep them up, and then carefully micro their healing so they don't overlap.  That is a LOT of AoE healing power.

Halcyon  -  TK Push - AoE anti strikecraft defense and Energy Aura  -  Boosts damage...with enough ships, the boost can be worth more than the cost of the Halcyon in firepower.

Progenitor - AoE Shield Regen + Iconus Guardians = damn hard to kill Advent fleet.  Some Advent use 2 or 3 of these in late game fleets.

Kol - AoE anti Strikecraft Flak Burst can tip the strikecraft war heavily in your favor.

Marza  - Raze Planet, Missile Barrage.  2 Marza with Missile barrage can destroy an entire fleet of cruisers.  Generally, only 1 is needed to kill a fleet of frigates.  Probably the most overpowered ship in the game right now.

And suddenly, when you start enjoying these caps direct powers, you suddenly have a use for other support capitals to either counter them, or amplify them, like the Revelation or Dunov.

Does the game get to this stage often, or is it necessary?  No, not often, but if you ever get a chance to fight a late game player who can carefully micro a complex fleet, it is impressive.  Late game Advent battleballs can be extremely tough to kill, and they use 6-8 capitals making full use of synergies, but they have tons of frigates too, because the capitals by themselves are not that tough.

You generally have to play bigger maps to get to this stage of the game.  In 30 minute to 1 hour games, it is probably better to just make frigates, because you don't have time to develop a high technology, high level cap fleet in that time.

You might also find some ideas in this great thread that SageWon has kept updated.

https://forums.sinsofasolarempire.com/335807

Personally i believe that caps should have serious firepower. i mean bristling with all types of weopens that could seriously be a fleet stopper if correctly microed, hard to balance, but i would suggest making them cost more in every area. If it is a flagship it should make an entire enemy fleet get scared it is so powerful.

I know though it would be hard to balance and would thus make caps probably OP.

Why would you ever want 16 radiance ships?  Ever seen a malice/cleanse combo with radiance and mothership?  Or how about animosity/vengeance combo with radiance and rapture?  Oh, and let's not forget that throwing a Halcyon in is worth it just for the aura alone late game.  I hope I don't need to explain the reason why you'd want at least one revelation.  I'm not a huge fan of revelation, but I always make sure I have at least one.  Advent are easily the only faction which should diversify between all its cap ships in almost every situation.  They just have such an awesome synergy.

Now, that's not to say radiance is bad at all.  In fact, by the time I hit 16 caps I usually have more radiance than any other cap, just because they're the toughest to kill and have some of the best firepower.  However, I have lots of every other kind in support to back these guys up.  Also when you have three or four shots of cleansing brilliance you can really cause your enemy a scare.