Why does Eviscerate hit like a pillow?

Overall, we think rogues do too much passive damage -- autoattacks + poison. We want to shift more of that towards their specials, which will let both the finishers and the generators hit harder while keeping sustained damage about the same. It might mean less-skilled rogues do less damage by comparison, but that's not really a bad thing.

Q u o t e:
If you are going to make rogues do more damage with specials, won't that make them more "bursty"?

That's the risk, but from a broader perspective you're identifying the problem: more damage on specials is more fun and generally requires more skill than lots of damage from auto attacking, but can lead to more burst. That doesn't mean that tons of damage from auto attacking is a desired goal though. Neither extreme is fun.

In Cataclysm, when health pools are much higher, then burst as a PvP strategy just isn't going to have the same strength it does now. In LK you can get someone close to death in a few globals, and in fact you need to, because if you don't the healer is going to have them back to full again. In Cataclysm, sustained damage even in PvP will be more meaningful, because you're trying to shift someone's health towards an endpoint instead of flipping them from 100% to 0%. It should feel more like a tug of war over health. In that environment, burst can still be good for when you need to actually get that killing blow, but it won't be the only strategy.

Rogue burst is also scary today because they can deliver it while a target is chain stunned. We've also said that's not a particularly fun place to be (for attacker or defender) and we need to shift rogue defenses away from short-duration immunities (which includes the stuns) and more towards being able to stand toe to toe with other classes a little better.