While I'm sure this is the wrong place for this comment, it seems to me that viral ships are insanely powerful in the hands of the AI, due to not having a ship cap to stop them from replicating. While in the hands of a player, you can make half the cap, and then they make the rest on your own..... sometimes...
But even if they work perfectly, you only ever get the cap, never more, while the AI can go from 500 viral ships to 1,000 viral ships if they attack and win. Meaning that viral ships in the players hands, when at ship cap, don't actually use their viral-ness. Or if they do, it's hugely lowered. And that can be a problem too, because if you are over cap, and then a planet gets smashed, you can't just make more to bring it back up, you have to move them from somewhere else.