So you posted saying your sure this question has been asked before, yet make the post about it instead of useing the search function. Yes this question has been asked ever freaking week since hard launch.
The answer:
Bariss has 2 parts to her heal. First she equalizes everyone's health.This is not considered a heal. Example if you have 2 toons. 1 at 100%, and 1 at 50% she equalizes it and both toons will now be at 75% health. Then she heals 15% of their health. If they have immunity they do not receive the 15% heal.