until lvl.80 comes out and we get the new pvp gear with super loads of stam... pvp has become a burst fest. arcane mages and ret pallies being the most powerful currently in terms of burst ability.
literally, my 460 resiliance, 13k hp is gone in less than 10 seconds from either of them. with my pve gear on i'm dead in like 4 seconds, and I'm currently spec'd demon form (for soloing onyxia and to simply test the spec out), so I have ALOT of damage reducing talents o.0
I've been told that for us locks, destruction is currently the best pvp spec (while at 70 at least) due to being fairly powerful in terms of burst capability (though not as powerful as others for burst damage)