Any reason why Sion isn't nerfed?

because he's easy to play against, if your team loses to int sion then they weren't really trying to win in the first place, int sion and tryndamere players are a lesson to selfish teams that they are garbage and need to learn to play the game properly if they want to continue forward. i.e helping your team when there's a 911 emergency in the top lane

His r definitely should be nerfed

Because he's the only viable tank (Is cho still viable) toplane and it's easier for riot to leave as is, so they don't have to fix their game. As you said he can do damage, resists (tankyness) don't mean shit atm when true damage is so rampant, also helps that he gets infinitely increasing hp the only counter to true damage.

He also is not the worst against all the bullshit you find top, viktor is just the latest problem in a long line.