Could I voice my (limited) opinion on Sion?
I feel he's far too magical. By that, I mean I never liked he has a point and click stun nuke that's supposedly him "staring at an enemy so hard that it damages and stuns him". That's DnD Wizard territory right there. The same goes for his magic shield, that too is something I feel does not belong. It's a great concept imo, but I don't think it belongs on Sion.
Sion should be a sluggish brute that ignores attacks and cc designed to hold him back. He shouldn't be fast, but he should be unstoppable. If he sees a target, he will shamble towards that target and he will use whatever he gets his hands on to pummel that target. Axe, or a chopped off arm, or bare hands doesn't matter.
Of course, this is from a person doesn't play Sion much. But why else do you think I disliked playing him?