I think this is pretty debatable. It boils down to how good you think it deserves to be against Cunnings, especially considering it usually dominates most Resilients and Fierce creatures.
Giving it a non-Distraction-cleansing slowing move would make it less useful against Cunnings, but it would still leave them as setup fodder for whatever comes next, so it wouldn’t be hard-countered by them.
Also some Cunnings don’t have multi-turn Distraction or rend-resistance, meaning it would still deal a lot of damage to them (e.g. Smiloceph, Velosrhacos, etc).