Originally Posted by
DarthKeller
Affliction, hands down.
Here's Affliction leveling: Dot first mob, dot second, third...fifth....12th (yup, got that high before). Refresh dots as they fall off, watch your enemies die
You can finish "kill X of Y mobs" in minutes, much quicker than any other class/spec I've ever seen (and I have one of each class).
Any "group" quest, so long as it doesn't require 5 members, can be solo'd by a good warlock because of the health you get from Fel Armor, so there's more quests and more XP than most classes can get.
Really, I can't think of a single reason not to use affliction