Game Mechanics: Heal did not take hold

[entilza]

Bump! OK, I am now getting this "Heal did not take hold" message. Getting a bit more scarier at the higher levels...

So far only a couple times now but more recently, this looks to be a hard issue to debug but my friend and I seem to have found a commonality:

So far it's happend a couple times when fighting a 'Shaman' type mob, and when a dot is on my tank. Tank is also a monk if that changes anything. So far it's been the poison dot. Haven't fought many dot casting mobs so it might be more evident sooner.

If others have experienced this, please post the situation to help solve this bug.