In the item description, it is written “Your Poison Damage Modifiers also apply to your Skeleton Rogues”.
Firstly : does it include all sources of “poison damage modifiers” that apply to me (like items, idols, passives from skill tree (node such as “Three plagues” from Lich)) ?
Secondly, what is considered as “poison damage modifiers” ?
To me, it would include :
Poison damage ;
Poison penetration (through three plagues nodes for example) ;
I believe it’s just poison damage modifiers, since the other ones you mention don’t change the amount of poison damage you do, they change the amount of poison damage the target takes.