It's not OP in the current beta, and with massive health levels of other classes, resistance mechanics, abilities to wipe/remove dots, etc.
I've been fighting against warriors, death knights and others in the beta and you have to remove your mindset from where we are now in Live, to where we will be in the expansion. When you begin live, your health has already dropped. Warriors on the other hand have tons more health and dual wield 2-handed swords .... and be prepared for being death gripped by zillions of death knights.
Dots, and warlocks, in that context are by no means overpowered. The opposite, in fact, as any beta tester who does pvp will now tell you. (Resilience too of course...). In PvE, half the time your dots don't even run their full duration, thereby gimping their overall damage, too.
Bring on some form of dot-scaling with crit and haste. The EU and US beta forums have had some great suggestions for this:
WoW-Europe.com Forums - Warlock
and
WoW Forums - Warlock Discussion