I found a pretty nasty bug on one of the uldyssian mini bosses
https://www.youtube.com/watch?v=dm3OMBOFBoUIn the video, I kill all of the npcs in the area, except for the last one, Korlic's Defiled Memory. This npc seems to go immune to damage. This happens as soon as I enter from the previous mini boss room. The immunity will not drop until Korlic does a leap/jump animation which seems to reset its state. This exact enemy had the same issue on original d2 as well and would get stuck from time to time. I think it has to do with the enemy getting "stuck" mid jump animation, and when Korlic is in the jump animation he cannot be damaged. Then I basically just have to kite him around and wait for him to jump again. There have been times where this takes up to 5 minutes, and it's really killing my motivation to keep farming this Uldy.
Notice in the video that i am able to kill everything else pretty quickly, and at the very end when Korlic does his leap animation, the immunity drops and I kill him almost instantly.
Korlic is taking me longer to kill in some cases than Uldyssian himself as a result of this bug. This is reproducible for me every single run at this point. Going back to town and then coming back does not help. Dying and coming back does not help. Teleporting away from him does not help. Leaving him alone in the corner of the map does not help.
Easy Proposed Solutions
1) Make it so Korlic is not the npc that needs to be killed to open the portal to the next area.
2) Remove Korlic from the fight entirely