I tried this devotion on a recent build and found it rather disappointing. It was a ranged WPS build with high CDR.
The problem is that you can’t really control where the nullification happens. It’s effectively useless against packs of heroes. You also can’t cast it on yourself. It’s only good against the Herald of the Flame. I even tried putting it on ABB to control it better, but it was still bad. If a Regenerator hero is hiding behind other enemies, ABB wouldn’t reach them and the nullification would be wasted on the front rank.
Arcanist nullification doesn’t have these problems because you can cast it exactly where you point your mouse.
I think the neatest solution would be to simultaneously cast Cleansing Waters under the player as well as under the target. That way even if you fail to nullify your target, you could still nullify yourself of DoT effects. Also maybe buff the radius a bit.