I go even go aff/demo hybrid and use a spec like:

http://www.wowhead.com/?talent=IVMriMckVdZfxczIrzc

for extra lol effect. Would loose instant howl of terror, but my dark pact / life tapping would be INSANE... Since the imp will get 100% of the mana I gain from life tap, the efficiency of life tap would actually be doubled. Then combined with improved imp for extra hp buff goodness (keep paladin (or other lowbie) alive longer).

Dark Pact + Mana Feed = Nasty.