Cool thanks for giving a response.
When I encountered the bug for helwyr I did actually move him around quite a bit to no amount of success. The mob kept passing by. I defended south gate with him in my second run so I didn’t test for the issue a second time. He was being a bad boy.
The immortal Tok Haar - I have a theory that maybe you can test. Can a wonky internet connection or some hiccup in computer hardware cause it to miss the check that’s supposed to kill things that reach 0HP? The Tok Haar in that particular scenario dropped to 0HP and continued to hit the barricade for 75% alone (the barricade was taking damage with no other sources nearby). And then he mysteriously vanished. During this time he was completely uninteractable.
I can attempt to replicate this and submit a report ingame later.
Our calculations are done serverside so it won't be anything to do with your connection, so please don't stress about your setup. It'll be a weird glitch in the death code, possibly in combination with some other process. Worth considering things like abilities used, any items you've activated, or potions you're using. I'm doing some digging today, see if I can find it out.
You lose nothing other than time if the event fails, so if you're encountering this problem just home tele and restart and hopefully it won't happen the second time around.