"Player deals critical hit" doesn't work with Variables and other Global Triggers?

I don't know if this is a bug or it's supposed to be that but I want to make an Life Steal Enchantment where you get 15% of the Damage you dealth if you make critical hits to the Mob. 

To get the amount of the Damage I'm using another Global Trigger that triggers once you attack someone or before Entity is hurt and set an Player Variable to 15% of the amount of the Damage.

Then the Critical Hit Trigger for the Life Steal Enchantment add the Amount of the Damage where I got the 15% out of it as Health. But it doesn't work at all. Nothing happened in the Game.

Know someone how to make it to work or is it not supposed to be work?