It's passive, so it should just be 'on' if you have the skill. He was able to get the skill to level 3 somehow, so it is active in some respect, but no stats show for regeneration, and no additional health seems to be assigned when drinking potions or any other health-adding actions such as bloodlust.
I believe that it 'was' working before one of the last few updates. I'm not sure how many people have that skill to test it.