Soul Leech is a warlock talent that heals you every time a certain single-targeting ability damages an opponent.
In patch 5.2, it will change from healing you to placing an absorb on you.
Ive really been wanting this for monk's Healing Elixirs and if anything it would make more sense to me to give it to monks than warlocks. It can be hard to control healing elixir since it always procs every 18 seconds even if you are at full health where soul leech heals a portion of your damage so it's evenly smoothed out.
It's cool that Healing Elixir will get a slight buff but I still only see it being most popular for pve mw