Our group ws the whole fight. Unbridled Wisdom Absolute Terror the Unbridled Learning Absolute Terror if needed toward the end. Unless there's a hidden gimmick (not noted anywhere), this mob doesn't take extra damage during phases. I would say if your're not using the new SP + Absolute Terror when you run with a blu, then that's doing it wrong.
If u did ur WS midfight u did it wrong and if u did near the end as usual it's normal that he takes higher DMG,next post a 99999 victory smite from crackclaw rofl