Hm

I think I'll go with the lock, actually I'm considering a build like this:

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

That is Aff / DS.. (40/21/0)... I know it sounds like a weird build, but then I have the option to use Dark Pact if there are phases where mana is a problem and then I can DS either succubus for Affliction with +15% shadow damage or Void for increased health regen. I like my booster to cast instant spells, so I probably won't miss UA too much anyways.