Hollow Form info

I am playing Hollow Form and cannot find information about how this skill scales and more info on how it work.
I figured Garukhan's is not working as is not hit by me. I suspect rarity dosent apply too because i am not killing the enemy, my astral self does ? now does this astral self is considered me or not ? its so confusing with no explanation . maybe GGG can add more info how hollow form works ?