My rogue is 62 atm and i swap between the specs every so often, assassination seems to be the only one fast paced... combat and sub seem slow and clunky, combat seems to have a big ramp up time with revealing strike and that 30% damage passive, sub seems to be energy starved alot but i think thats because i dont have the slice and dice talent yet. however, assassination seems really fun, i do a mut + rupture on a couple mobs and im swarmed in energy on mob pulls. does this change at 90 when you can stack haste or does it pretty much stay that way?
second, is rogue pvp at 90 that bad? i'd mostly just do bgs and 2s on it, nothing super serious
People generally consider Assassination the slow-paced spec at max level because energy regen is quite low and Mutilate the main move you spend all that energy on is quite expensive. While Assassination does have the most downtime I find it not too much of a problem because while you wait for your energy you have other timers and things to keep track of. The biggest bulk of your downtime is when you have 3-5 combo points and you're pooling energy before you Envenom. While I'm pooling and calculating if I can get a 5 combo point Rupture rolling the next time it falls off, I personally have the feeling I'm actually being active and doing something. But that's just my own personal opinion.
Combat has a few cooldowns that greatly increase your energy regen and that makes for some fast-paced gameplay, but outside those cooldowns it's much the same, waiting for energy. But this time you don't really have a whole lot of things to keep track of. Because of that Combat ''feels'' much slower to me while in reality it has much less downtime compared to Assassination. Pooling energy before having to reapply Revealing Strike feels like an eternity.
Long story short, currently at level 90 all specs quite suffer from downtime and waiting for things. Gear will fix it, but until then you just have to enjoy seeing your passive damage rack up.
Rogue PvP could have been better but right now only Warriors, Hunters and Warlocks seem to do well. In comparison everyone else is a bit weak. Rogues aren't really massively broken but there is always room for improvement.