Improved imp is a waste of 3 points as is Improved drain soul. Use only 1 point in Shadow embrace and get 5 points in fel domination if you want to go life drain focused spec. Something like this: http://www.worldofwarcraft.com/info/classes/warlock/talents.html?1500222512231100000002350030033050100501300000000000000000000000
Personally, I'd rather shadowbolt DPS, so I'd go with a destro/affliction spec, but that's just me. --- GT: Seven Signz (>'.')>-I===> "It's time to slay the dragon."