He is in line for a rework, last I checked.
Clearly you have never been bothered by mid game nuke Sion or late game invincible hyper carry Sion.
I hated AP Sion. It was a good runner up for "most degenerate thing that has ever existed in this game" although the 4 second stun Kayle probably owns that title solidly.
I liked AD Sion because he had to autoattack people despite being immobile and having a short range on his stun. He was never invincible because he was very easily kited and worn down. As a result his item choices had to be adapted to the match to get him the tools that he needed and he had to enter teamfights with smart timing.
EDIT: The difference between Yorick and those champs is that Yorick is not fun to play as. He gives you very few decision points. Those champs might be toxic in some ways but at least playing them isn't boring. Yorick is toxic to both the player and the opponent. That's a pretty big failure.