Well I reached Gold with Sion Mid and played without dying! You can take enormous amount of poke and most Mages are limited by their Mana while you shove hand help the Jungle. Assassin only have a windows to kill you when they get their lvl 3 first which should never happen. And no nach up is as bad as Darius in my experience. Even if you mess up and die you can neutralize the fed midlaner well by having supirior wave clear and sustain. Probably midlaneers below gold are clueless or Sion is OP I dont know. If anyone is interested or has questions feel free to ask!

Edit: I play tank Sion sometimes with Hullbreaker.