Riot, it's hard to have faith in your balance team. You screwed over mana-itemization, yet...
You left manaless champions as they are. Now if this was a move to even the tables that's fine. But it clearly wasn't. Mana-users and Non-mana-using champions have been on a relatively even playing field for most of last season. Often times it'd even feel like the favours are tipped towards the champions who can just spam their spells without any consequences.
So you decided screw over most mana-using champions, which, if you had shown foresight and adjusted the numbers of every individual champions in the game, that'd be fine, but no. You didn't do a thing at all to make up for the change. While mana-users had to put up with Chalice being garbage now and have to adapt by going buying Morellonomicon (and only the Morellonomicon...), those who are resourceless or simply used energy remains completely untouched. They're free to instantly clear waves and spam their spells whenever they want.
Now let us forget about the issue of your favoritism towards resourceless champions for a while...
You messed around with the balance among mana-using champions as well. Not every single champion were equally screwed by your changes. For instance, 
is occasionally affected depending on his build (believe it or not, there were some contexts when Chalice WAS superior to Catalyst), 
is minimally affected as well. But then you go to 
or 
who only stuck around competitively thanks to Chalice. And what of 
? Chalice/Athene's was his core item.
And don't give me your "just manage your mana!"-response. If you're managing your mana, chances are that you are hurting your own damage and farming. Champions who don't have to watch their mana nearly as heavily are capable of doing all that and more. Chalice is only effective if you also spent a buttload on mana. Neat, so the only time I'd want a Chalice is...when I don't even need it anymore.
All of that and...with Morellonomicon replacing Chalice, there's likely unforeseen consequence with sustain-reliant champions. Again, foresight.
PS - since I brought up . As someone who used to play him and kept track of every change that affected him, you...nerfed him back when he was barely played anyways, you nerfed MR runes which hit Galio significantly more than it hits everyone else, you continuously screw over MR itemization which also hits him more than anyone else, and you continue to add more and more KNOCK-UPS and STUNS to every single new champion...which also makes life for him a living hell, especially when his R can only be pulled off with a Flash to start with.
If you hate Galio that much just rework him. But don't pull a Cassiopeia on him by turning him into some sorta squishy poke mage and rationalize how it somehow fits his identity more.