First boss in act 2, Rathbreaker stopped using any skills after being lured down the cliff

The boss was lured down the cliff (down sideways), and then it went back to the top of the cliff. When it got back to the cliff and I was still down there, I saw it regenerating life. Then I rushed back to the cliff to prevent it from healing, from that moment (<50% HP), the boss stopped using any skills that it used to until I killed it. The boss, Rathbreaker, was just trying to approach me and hit me with an apparently default attack.

same here. did 30k damage sitting next to it. every now and then it rolls over, then returns to same spot.

hyenas respawn... so no end to fight.

you have to respawn at checkpoint to reset the fight.

maybe they expect walls to stop you moving out of small arena.