I would say the main issue with trolls is the normal ways of avoiding damage don't work if you're cornered. If you try to block, you just get smushed into a wall. If you try to dodge roll, your weapon catches on the log and you get carried with it and you still take damage.
There's definitely time to react otherwise. The enemy is fun to fight otherwise.
Yeah, you could also disable weapon collisions during dodge rolls, but that would also the player to bypass enemy blocks, which could be interesting, or maybe too powerful. I can imagine there would be physics engine issues with a weapon "phasing in" to a different weapon.
Trolls taking more body knockback won't help because often they often have their back up against a wall as well.