There is a huge thread rolling on the forums that starts off with a reference to Tom "Kalgan" Chilton talking about PvP at BlizzCon. There, he said that Warlocks (and other classes) weren't necessarily balanced for 1v1 PvP-- instead, the classes are balanced for arenas (moreso 5v5 than 2v2 and 3v3, but those as well). This, of course, brought a chorus of anger from players-- considering that lots of World PvP is actually 1v1, why should any classes get a break that way?
Kalgan, in return, basically says it's one or the other-- there is no way developers can get everything balanced all the way across the board, so they tend to balance as much as possible, which leaves some places where classes are more powerful than others. A little bit of OP, in other words, is acceptable, as long as the other classes have their place to shine as well. I found this to happen at BlizzCon as well-- when the designers explain their position to you, it seems completely reasonable. But when you go back in game, and a Warlock deathcoils you into oblivion, all the nonsense about balance and 1v1 vs. other situations goes right out the window, and you just want them to fix the game again.
At any rate, big changes are coming, says Kalgan, both in 2.2 and 2.3, in terms of class balance (specifically the DoT/Resilience change and the Mace spec nerf). As Boubouille says, it's looking more and more like 2.3 will be a "big" patch, with lots and lots of changes and revisions for each class in the works.