I watched the whole video. Great idea to add the screen grab video for documentation! There definitely is some sort of 'continuing' serious conflict between the game & Immunet.
"Yeah, that process 'normally' does not continue to use up that much system resources for that length of time!" Weird!
Have you tried to contact the game's developers to see if Path Of Exile has caused problems with other AV's & if there's a fix/workaround for that?
This just a guess on my part but some games do use one or more Windows Temp file directories that might also need excluded. That's something else you could ask the game's developers.
One more thing you could try is also disable 'Monitor Program Start' in Settings to see if that makes any difference. You will lose some of Immunet's efficacy by turning off this important setting however.
Like I mentioned before, I do wish a support technician would get involved with this issue but I'm not going to hold my breath on that happening!
Best wishes, Ritchie...