As a note, as a UA Lock/S Priest/Resto Shammy don't be shy to use SP when bursting, a good insta SB -> SP combo is much more effective than DL.
Also, even with rogue, most locks are SL/SL for 2's. The only 2 setup i would go UA is with S Priest, and i have not played this setup since S2 when my priest went to Iraq.
*** Information added 5 Minutes and 20 Seconds later... ***
Update: Checking
2v2 Rankings - Warlock - Arena Junkies it seems that this days Warlock/Rogue is better or at least as good as Warlock/Priest, at least its more represented in the list being only second to the overwhelming amount of warlock/druids.