Jewel Crafting
Jewel crafting still stands as THE best profession for warlocks. The functionality of prismatic gems is amazing. Lets look at the math:
All warlocks will be running [Chaotic Skyflare Diamond] in 3.1. To satisfy these you need atleast 2 blue gems. the best option for a blue gem is [Purified Twilight Opal] which yields 12 spelldmg (assuming demonic aegis..
Assuming all other gems would be [Runed Scarlet Ruby] which is 19 spelldmg.
So We have 32*3-(19+12+12) which is 53 spelldmg + the option to choose the best socket bonuses to use, which is a min of 67 dps increase using the 40-31 scale factors