I'd keep the warlock yeh get Curse of the Elements for 13% increase to damage or switch out the pali for a deathnight and spec for ebon plaque bringing another 13% increase to damage
or yeh could switch out the warlock for a balance druid and spec earth and moon for another class that can increase damage by 13% they dont stack :P

Really tough to beat a straight 13% increase to dps especially when everyone in the group has got a blue bar