Guys, Sion needs a little bit of help
And don't get me wrong, I love Sion. He was a wonky looking undead zombie at first and then Riot reworked him and made him into a terrifying beast...at least he is terrifying until you realize how weak he is. He is slow, lumbering, hulking, giant with lots of cc in his kit but not a lot of damage. In our current meta, where do we put slow, lumbering, hulking, giants with lots of CC? Bot lane....as a supp...Sion is/was supposed to be a top laner.
And sadly as a support main I can tell you that he isn't actually THAT bad as a support. You have a knock up at level one that can also be a slow. You have a shield that scales with health AND ap, and passivley gives you health for cs and kills/assists that can also be used to do damage, you have another slow with a bit of armor shred, and you have ANOTHER aoe knock up....It's A LOT of fun to play him.
But if you want to play Sion, why not play Thresh, or Blitzcrank which is essentially do what a support Sion does...but better because they are literally DESIGNED for it.
And then there is Sion's passive. Nigh to useless in top lane. You MIGHT get to even the score by killing your attacker with it, if you are lucky you MIGHT get 2 kills, but that is so freaking unlikely. In Bot lane it is actually useful cause you are a tanky front line and if they kill you, you revive and can still do damage to people, but even THAT aspect of the passive is nerfed by a capped attack speed...not that he needs to have a freaking 100% lifesteal passive AND be able to get attack speed...but still idk