Spore is supposed to be the Korath's super ability. If you nerf it too much w/ cost or prerequisites, it'll no longer be super. It's supposed to be powerful, just like the others' super abilities. Like if you spore the Altarians, you are now at war with every good civilization in the game.
I do think the AI could improve Spore defense to be more human-like, but the AI *does* already create defenders with 0 weapons, even in DA Gold. I'm dealing with that right now. Like if you saw a move-3 Spore ship and it was 4 parsecs away, alone, you would rush-buy a tiny hull, weapons or not.
Spore Weapons are a powerful Super-Ability also in end game.The simple fact that you can make toxic worlds and erase the entire population of a planet without losing a single soldier is simply huge.
Since GC2 was released rush strategies have been always a winning strategy because AI doesn't build too much armed ships in initial stages, now with Korath it is simply easy to erase entire civilizations.In my first game with this civ i had destroyed 2 big civs in 100 turns, building just some armed ships and only Spore Weapons.
Based on my experience they aren't game breaking when other civs have some ships to defend themselves but at the beginning it is too cheesy as Korath to destroy other civs with Spores.Spore Weapons is a tech so powerful that its more fit for a mid game at the beginning it's just like having Terror Stars of GC1 which are not available to the other civs.