Before you bring to the table the recent nerf he got (-20 damage from Q) i would like to point out how overloaded his kit got over the years to allow him to be viable in this broken state he is right now, low risk/medium high reward.
Instead of riot coming up with a proper rework, they've decided to add more functions to his kit like the recent 25% armor reduction debuff after 4 consecutive spin hits and the true damage passive assigned to his ultimate towards the champion that's marked as the villain"
His passive also has another function where if he is below 25/50% health his regeneration is doubled. It is hard to deal with a champion that's basically an immovable object due to this passive and the fact that he is manaless but you could at least farm and sort of outscale or go even with him, which is not the case right now due to how his kit revolves around combined resistances, damage reduction and tenacity from his W, a slow cleanse that has an extremely low cooldown and potency with his build path that revolves around health and cdr in the shape of the black cleaver.
Now, what i described is his durability but with the "recent" fore mentioned additions to his kit, he can't be (partially) ignored because he is such a high threat to anyone marked by his "villain passive".
So in a few words, we now have a champion that creates too much pressure while being able to shred tanks and squishies alike and takes far too many resources and time to be brought down in a teamfight.
I can't come up with any suggestions in order to properly tweak his numbers, kit functions, but one of the following has to go;
1. Early game bully
2. Late game hyper-tank teamfight shredder