if you have a bard or summoner, they can bind him, dragoons can slow him. Swiftcast + stoneskin + sprint is what I do. Or, if you are feeling daring you can run behind him, though those cast times are rather stringent and you need to be there with time to spare without him turning around and sometimes you still get hit behind him. I suggest the run behind if you are in DL gear as you will likely survive even if you get whomped. However running is almost always effective, doubly so if you are stoneskinned just in case and someone slows/binds the boss to give you a head start.