Between Arenas, V'Ming spends his time as a lock laughing ominously in AV, tanking Olm with his own minions and pondering troll fashion from Zul'Aman. He's recently started to plumb the depths of SSC with his 0/21/40 build and bragging about 8k shadow bolts.
Sneaky, backstabbing rogues and warlocks seem to fit naturally into the evil mold - with the latter summoning demons from hell and all. Unlike rogues, who seem more like common thugs and hired hands, warlocks are more akin in flavor to evil masterminds, orchestrating doom behind the scenes and manipulating their minions to get the dirty job done. Incidentally, it was a warlock who got us into this Horde-Alliance mess.
Like Elizabeth, who wrote the rogues' version of "How to be evil", I'm not a mean, vicious or even evil person. In fact, if you met me in a dark alley, you'd probably invite me home to meet mom. So how do good people like you and me play this deliciously evil class to its full creative potential?