It's easier to get high dps with affliction.  Affliction isn't so gear reliant.  apply ur dots... be sure to spend 2 points in imp soul siphon.  drain tank.  high dps... using hardly any shadow bolts, i am always #1 in raid and instance dps, unless there's a good combat rogue.  Also, you'll never have to worry about mana... via lifetap and drain life/dark pact.

Drain Tank FTW