Pirates and nomads have a BIG disadvantage... they can't colonize planets!
This makes them MUCH harder to play than normal races (btw, remember to setup your empire file with "normal" if you don't pick "pirate" or "nomad" otherwise you're REALLY screwed!
)
I'm not so sure about the Talisman; on the one hand, the lower level ones are bigger, but on the other hand, they are available at level 2 of religious technology! Talk about a talisman rush!
(I guess though that since they crowd out weapons on smaller ships, that makes them impractical until you've researched some fairly large hulls anyway, but I still don't think it's quite enough to balance it out...)