I definately might look into demonology. Affliction offers WONDERFUL croud control. Drop DOT's and Siphon Life on each person and drain tank each one, fully able to heal whatever they dish out if you're not too far below them. Having a voidwalker out only benefits you, too.
However, I think it'd be nice if your voidwalker could actually hold aggro while you attack something like it did at the low levels, and could actually do damage. Master Demonologist could be great in the middle of a fight if someone kills the pet or you have to sacrifice it (voidwalker).