In terms of weakness, Weakest classes would be Warrior, Hunter, Warlock, in that order. Warriors getting the shortest end of the stick. (Just how i see it.)
Demonology is iffy, haven't really played around with it. But inside Meta, between aoe's, immo aura, hellfire, etc. Makes you into an AoE god for the duration, aswell as being nigh-unkillable, with a decent chunk of resilience, and/or a healer.
Affliction lacks pick-up burst in a very bursty breacket, Probably better suited for 3s/5s.
Destruction can have insane burst, (ie; Chaos bolt, conflag, insta-soulfire, Tazik, etc.) coupled with decent control, shadowfury/succubus.
Just my opinions on the specializations, Just couldn't really get demo/affi to *work* in battlegrounds, or 2s.
Overall, warlocks are lots of fun to play,
Oh i see. Well i am also considering a hunter.
Hunters do great in battlegrounds, can do well in arena, They just lack most of their defensive cooldowns. (Deterrence, 78. And master's call, 74.)
We've got Roar of sacrifice. (Tenacity pets only, Unless you are BM, then Cunning/Tenacity.) And disengage. Even with both, We can be dropped in a cheap shot, and a decent rogue would be able to just *sit* on us, even with disengage.