So far, the best talent build i found for RAID is 0/21/40 :
http://www.wow-europe.com/fr/info/basics/talents/warlock/talents.html?0000000000000000000002350010133200100000000505000512200510531050 (or anything around that, but keeping the major points such as sacrifise)
This enables any 1/2 epix warlock to crit for over 7000 dmg if you have a shadow priest in the raid. You lose the use of the imp by sacrifising the sucuby, so not to use in MT group.
I also advise every warlock to have the talent "improved shadow bolt". I a raid with 4 warlocks, you almost always have the debuff on the boss, incresing your shadow dmg by 20%.
Watch out though, any warlock using this spec without KTMthreat meter is comiting suicide, and is leading the raid to a wipe. Chaining dmg without a threat meters there will 'enable' you to pull agro off any tank within seconds.
I promised the GM that I would try my best to help out with raiding, been a former admin of this forum, and of your guild. So i though the first usefull advices i could give is to warlocks, since its my class ^^