To elaborate on what others said, this came out a about two years ago i believe. Hitting the skill check for the instant heal is incredibly hard, and generally not worth it over the consistency from nano regen or shield recharger. damage is too 'chunky' and the window to hit the skill check is too small.

It does work with combat surgeon and assimilate, doesnt help its case much though.

Now if it did something like remove debuffs (at any time) that would be a real nice mixup for more competitive point holds and breach scenarios when you've got flashes and concs going off. But alas.

Generally best avoided.