Instead of looking at champions, look at the items.

Damage creep has been at an all time high for several seasons. You constantly increased the damage on items, gave stats more accessible by putting 3 stats on 1 item. Lifesteal has made champions so hard to kill to the point ADCs can 1v1 assassins.

You have ADC's melting tanks, and anyone else if they are protected. It isn't the champions themselves, it is the items.

Shields, CDR, lifesteal, crit chance, attack speed, damage. So many items that offer several of these stats on 1 item.

Look at runaan's for example, what used to just be 70% attack speed, only used on select few champions, its now bought on most current ADCs IE got dmg increase, crit chance up, BT got dmg increase, and a massive shield, and increased lifesteal, Stattik got a damage increase, higher crit chance, with only a little AS decrease.

The list can go on, most of the balance changes that we are facing now, have been from the ADC update, maybe not everyone things that, but in my opinion it was. Yes tanks were prime before that. but all that needed, again, was item changes.

The same for for mages, however this has somewhat been the same for a few seasons. (disregarding stacking passives in early seasons) avg 500-700 AP

It is time that you tone down some items, before adjusting the champions. Because if you looked at the items, it would probably somewhat balance the game beyond just trying to balance the champions.