The siege frigates do NOT need to be nerfed.
If you don't build a correct defense, and mass your fleet on the other side of the map, you're practically inviting him to throw in some siege frigates.
a) Hangar stations can build fighters, which are supereffective against small groups of siege frigates.
Even an asteroid can be upgraded with enough tactical slots, and hp, to survive 6-8 siege frigates on its own.
LRM type ships rapes siege frigates, and they are cheaper. Having a few of them a jump away is a cheap counter, and you can cover every planet they are one jump away from.
10 siege frigates costs close to 2 capital ships, or 22 to LRM frigates. Do you want them to be useless just because you don't have a decent defense against them?
I challenge anyone of those who have called for an nerf, to put up a replay where a small raiding party of siege frigates is raping a defended planet. If it isn't defended, then it's your own fault for losing it.
Edit: The argument that you did not have enough resources to build anything is invalid. The research costs are the same for both proper defense, and siege frigates in average for all three races. It also costs alot to build siege ships. Early researched, and produced siege frigates will cost atleast 3000-4000 credits. If he does have that much more credits than you, then you can't blame the siege frigs for losing, but rather your slow expansion and slow resource building.
My issue with the fleet cap is that the upkeep shouldn't be static. Each ship should add a small % of upkeep instead. If you lose a big army after a few fleet cap upgrades, you will still have that same big % on your income. This effectively lessens the chance of a comeback after a big loss.
Agree
About Fleet Cap...
A solid reason why they changed the Fleet Cap from planets to Fleet Research, IMHO, is that the game could be more balanced. I like it this way than the Beta 4 Version. It makes the player think about spending the resources correctly, having accountant like feel (sarcastic). In all honestly I like this version of fleet cap better than the Beta 4 version though.
EDIT The 2 paragraphs I typed didn't help make my case, so I erased them...
Now onto the Super Cannons. They need to be adjusted and a Ship that has similar Power needs to be able to be built (A Incredibly Awesome looking Supership). They both must have a limit, dependent upon the fleet cap, again forcing the player to really think about how he wants to develope his Empire. REason for not based on planets is because that the other fleet caps are based on research.