Firstly, the roll is still perfectly usable.
Secondly, the new changes removed the “3 mobs fight something at once only” mechanic.
Thirdly, Im not saying you did not give it food, but the image presented show’s its had it’s taken a beating and it has no food to help it out. I dont see a bow in the hotbar with healing arrows
Lastly, and I do not wish to come across as telling you that you’re playing wrong so dont misunderstand me, but that thrall is not well geared at all.
I threw a decent thrall into the wine cellar with food and high tier crafted gear and it had no issue, I was not worried about it at any stage of the dungeon.
Maybe you just had bad luck, but I personally think you presented your thrall with more than could be asked of it.