Is it really necessary to let him cast fear back-to-back seven times in a row? Can you please put a damper on this? it's quite annoying.
The Delving Departed doesn't ever *cast* a fear. He has a fear damage shield proc if you don't clear the adds - including the adds that spawn during the fight. Kill the adds instead of trying to burn through the mechanic.
the more adds are up, the more likely you are to be feared. Having a Crusader specced for Fearlessness, helps. Otherwise, crouch and walk and hope.