Every ship is strong vs some and weak vs others, but in general, end-game fleets usually look the same to me.
Keep in mind I play with Large fleet sizes and usually play TEC and exclusively single player since I like to take my time to expand.
120+ LRM for main firepower.
60 Cobalt for secondary firepower and sabotage.
at lest 40 Kodiaks for firepower
30 Hoshikos and 30 Cielos for healing and targetting for extra damage.
30 Gardas to pick up any anti-bomber slack from fighters.
30-60 Perchrons, each with 1 fighter 1 bomber squad.
20 Arcova with auto-target on, mostly to clear the rare minefield.
If I build Ogrovs at all, it's less than 10. Same with Krosovs and with Protevs, for neutrals.
However many envoys I need, if I hap diplomatic victory on. Otherwise I stop at 10 or so to get pacts quickly.
Fill in the slack where needed. depending on the enemy fleet, which usually means more LRM, Kodiaks, and Hoshikos.
As far as corvettes go, I haven't used them much(At least not while I was paying attention to what kills what in this game) so I'm not really sure how many to build yet.
2/3 of my capitols atr Kols and Sovas, in a 1-1 or 2-1 ratio, depending on what I want more of in a particular game. 2 of each of the others, and I fill in the extras with an even number of Dunovs and Marzas. (Haven't used the Corsev enough to decide how many I need, 2 seems to work well for me right now.
And of course my Titan.
-Twi