Well I'd recommend the following spec as a great all rounder.
http://www.wowhead.com/?talent=bxMhzhZZAGgzMtRhtVoIn terms of threat in raids, I recommend only using the following rotation (timings may be slightly out)
Vamp Touch, Power Word Pain, Mindblast, Flay, Flay, Flay, Mindblast
Vamp Touch, Mindblast, Flay, Flay, Flay, Mindblast
And keep repeating.
In terms of gearing, just make sure you cap your +spell hit then worry about +damage.