In frost spec I found that it is not checking the target of your water elemental. It happens to me that my pet is under attack (Pulled aggro) while I was in combat.
Once my target is dead, my character just stands there doing noting but waiting to get out of combat... Instead it should check the target of my pet, and to see if my pets target is in combat, hostile and targiting my pet.. If so, attack that mob.
Just an advice, for the rest, on hieger levers (above 35) I found this CC mutch better (More human, better survivabilety) than the default one.