This ability is quite clearly OP.
Just the massive slow + pull is already quite a decent ability (since CC is everything in this game...).
But, on top of this, it also does %max HP damage while it's on the unit. This ability basically makes Wazzmaka the best Elite killer in the entire game - easily able to Solo any melee Elite like Gabe or Dreadnought. I've seen my Ven. Dread go from full 7k HP to 2k in 15 seconds flat from Wazzmaka's ability (supported by ork infantry ofc).
It already drives Elite units to a crawl - why does it need to murder their HP as well? It's basically a guaranteed kill on any Elite Unless you can manage to disrupt Wazzmake (who, btw, gets + Movement speed while he uses the ability, making it very easy to dodge a lot of CC).