If he isnt a rager, then he is probably enlarged which makes his tanking more viable. Try to revert and dispel his enlarge. As long as he is wielding his polearm there is very minimal chance that he has a way to lag you, unless you are fleeing.

By dispeling his enlarge he will tank worse, and he may even switch to his other spec. If that happens, you get the chance to fight him without using his polearm. That may or may not be more beneficial to you.