Well some things i dont understand others i do. But you do this HC and respect for that and originality. I watch the stream sometimes. I would do something like this. I am not sure if the damage absorption from possession stacks with the one from the dark one proc, i thought not so i picked harbinger. Also bone harvest and much more flat vit damage. This is just what i would do.
https://www.grimtools.com/calc/62adMv3N
edit: also did devotions, no idea if this is good for hardcore just what i would do