I have allocated 5 points into the Reaper node on the Lich Tree so damage I deal should instantly kill enemies below 10% health. However I have noticed that this does not seem to work when the enemy is only taking damage from my poisons applied from Aura of Decay, even though it should still count as my damage as I am benefitting from damage leech.
As a side note, hovering over the % chance for poison in your character sheet to bring up the tool tip shows a spelling error: “Chance to posion on hit”
Hovering over the text poison chance however has the correct spelling.