A healthy way to nerf ivern is to force him to build his jungle item

Make his passive interact with the smite level jungle items where you cant interact with the enemy's side camps unless you have at least the smite buff level for it, and at that point it would also allow him to damage epic monsters.

The sheer fact hes able to just mind games his enemy early game AND rush a team saving item aka redemption is what is keeping him at such a lofty win rate. If you slow down what makes him oppressive then his win rate would probably stabilize into a more healthy area.