Zilean's passive nerf
Even after he was played by the pros, I never see anyone but me play him. And it's pretty obvious why; he's not that great unless you're with a full team. So why take his passive, one of the weakest passives in the game and that does literally nothing past about 30 mins, and make it weaker?
If you don't want to give him a new passive until the rework that's fine, but you basically just removed his passive and gave him nothing. And if he's played in middle like I mainly do, he almost literally does have no passive as it doesn't affect himself and no allies are close enough to benefit.