Share the Love Broken?

Share the Love is one of the few Dungeon achievements from WoTLK that I still haven’t completed, thus, I’ve tried to do this several times over the past few days, but it seems like it may be broken. I engage Gal’Darah, but he never transforms into the rhino which is required for him to impale players. I don’t recall that his phase 2 rhino form is related to a specific amount of damage dealt, so either I’m remembering wrong or there is something bugged about the encounter. Anyone have similar challenges with this boss recently?