in PvP Half the time I don't think it works at all, but here is an example
POWER LASH- deal 8705 Flame Damage, and heal for 12537 over 2 seconds. (unbuffed- I was buffed in the video)
I kill the target, am planning on getting a heal from the Power Lash and it never comes.. so I'm dead.
https://www.youtube.com/watch?v=46JKqn5bVrw
--- For a concussion build, it is your primary heal. I realize that is not the Meta or a sheild stacking Sorc so there aren't 10,000 other complaints. But it is my primary toon as I do my best to continue to play this game despite every other build I've run in the past 2 years being nerfed out of existence.
I realize the target had only about 4000 health and perhaps things are correlated to that (in this case), but they are certainly not written that way- nor do other class heals seam to work that way.