After reading some of Sparkuggz posts on his guide in the method forums he says that mastery is pretty much the way to go for destro since it scales so well. That haste isnt really worth it for destruction. Since gemming and reforging to mainly mastery its been a huge increase is dps for me.
Link to the page http://www.methodwow.com/board/showt...k-Guide/page54 . Seeing the dps their locks put out (yeah i know well geared) im inclined to stick to his advice on this.