It took some time for ICO community to adjust to new changes and develop most efficient early game strategies, and general consensus seems to be that balance is... well, !@#$.
Obvious reason for current state of balance is introduction of corvettes. They started as useless, then ridiculously OP, now slightly less OP but still not balanced.. at all.
So what's wrong with corvettes?
Their speed and generally high damage output. Player in suicide spot between 2 skilled players has now absolutely no chance of survival provided that he's fairly close to his opponents. Corvettes in large numbers rape builings, SBs, caps, LFs, LRFs... Because of their insane speed player in suicide is swarmed instantly and no matter how skilled he is he has no chance of defense. Bottom line is, suicide spot defense is now hopeless.
Seekers were considered OP because they countered LRF really well. What could they do beside that? Nothing. They were countered by: Flak, LF, fighters, SBs. Couldnt dent capital armor or kill buildings. And they got nerfed... Corvettes do everything what seeker did, plus they counter LF, can kill caps and buildings, including SBs, carriers, kodiaks and can target SC (SIC!). Compared to OP Seeker they're vastly more powerful.
Because corvettes counter LRF HARD, just as hard as pre-nerf Seekers did, while still maintaining very high general usability, whole early game balance is focused around countering corvettes. If you look at engegament between 2 skilled players, corvettes may not be the most numerous frigate, but that's only because whole fleet composition has changed in order to counter this single unit.
Usually early game fight looks like this: start with corvettes, counter corvettes with flak, counter flak with lf. And that's it, switching between those 3 frigates. In rare cases when you can get enough flak you can then switch to LRF to counter LF, but that's a luxury. So, you end up with fleet with very little DPS, which in turn causes balance problems with caps, especially TEC ones like Corsev or Marza, because of inablity to snipe them effectively. Low-dps fleets mean that AoE caps are too effective, because they can just sit near enemy frigates spamming their AoE.
So, IMHO, corvettes have 2 main issues.
1) make LRF obsolete
2) are too fast, too hard hitting, making rush 1v2 unmanageable. They can be at enemy HW almost instantly and pop SB before it builds.
Fixes:
ad 1) Increase flak effectiveness vs corvettes, slightly decrease corvette dmg vs LRF
ad 2) Decrease corvette speed and dmg vs buildings/caps to make them less murderous in 1v2s.