Originally Posted by Meloeth

Thanks a million Evolve for pointing it out. I assumed a UNIT_HEALTH event would be fired every time the units health updated just as on live so I have just checked how often this event fires which seems to be same as on live. But that code strongly indicates the UnitHealth(unit) function will update it's value more frequently then the event is fired!

I did some testing and the cVar "predictedHealth" is set to true by default. However when testing how my health updates I get the result that the health updates 2-3 times per second on my character with 23 mobs attacking me, both when the cVar is set to true and when it's set to false (with Instant Health loaded the health updated roughly 18 times per second). So it appears it does nothing right now, but it strongly indicates blizzard is planning to implement something similar to my addon right into the client. Would be awesome!