Why aren't there just 3 different balancing brackets?
Most of your issues come from trying to balance champions around every level of play. In a game like this, that's futile. The gap in ability, even between bronze and Gold, is massive. The gap between Gold and Diamond is so huge they may as well be playing two different games and challenger players are so mechanically advanced that it's once again like an entirely separate game.
So why, after all this time, have you not split up the balancing between tiers. It is impossible to balance this game when you nerf or buff based on what the top .5% need. At the very least I'd say give Master and Challenger separate balancing than the rest of us but ideally I think it should break down like this:
Balancing tiers
Bronze 5 - Silver 1 Gold 5 - Platinum 1 Diamond 5 - Diamond 1 Master - Challenger
I'm open to including Diamond in the Master-Challenger tier but that would be a community choice. Using these balancing tiers would leave you open to make the hard choices that you are always worried about much easier. You wouldn't have to think about the ripple effect going through all the tiers when you add 2 fucking AD to a champion. Most champions could return to viability in most tiers. Imagine a world where Katarina could see play in high ELO and Azir could see play in low ELO.
You have well over 100 champions and yet you only ever see about 30 constantly played. That's a lot of wasted time and resources, all these years spent building one quarter of a legacy. End it now, tier up your balancing team.
{{summoner:2}}