Holy shit...was helping someone with thorn bounty on the level 26 epic summoning pits amd ran into a knight that literally regen'd his health (not his shield, his actual health). So frustrating, I couldn't believe what I was seeing. It was the part where you enter the room and the Fallen are fighting with the Hive for the first time in the strike. We would knock his shield down, drop his health to like a quarter, he'd throw his regular shield up or go behind a pillar while we are reloading. He'd pop back out and as we are shooting him, his health would just start to regenerate, then bam his shield is back.