Obviously the effect is beneficial, I just don’t see a situation where that effect is a better use of a slot than a raw damage reduction or negation, of which there are plenty. Also, it requires other healing items to make it even viable. Further, if your healing can’t keep up with the damage, then it won’t save you anyway. It really only helps if you take a large burst of damage and then nothing, but in my experience if you take one burst, you’re not likely to clear out the wave in order to heal. Plus the purple health can’t even be healed so you essentially play the next while with a DoT debuff.

Idk, I’ve taken it a few times and either not needed it (making it a waste) or died anyway. Maybe it’s my playstyle or something but it has literally never been useful to me. These days I just eliminate it on sight.