I really belive the balance problems on this game are items and masteries.

I remember when Syndra had mana problems, and as such, had WAY more trouble spamming and bullying on lane. That way only good Syndra players could manage her mana and get nice harass. Then Lost Chapter came and as such no champion should run low on mana on the laning phase, and Thunderlords guarantees that your ult damage alone can kill anyone.

Twitch used to be a single target late game monster, but since he cant be realistically killed in lane because of Warlords and Runaans just means he hists 3/5ths of the enemy teams, kills 2of them in 2 seconds.

Hecarim shouldnt be able to 1v5 late game, but the item synergy of Triforce, Spirit Visage, and Courage of the Colossus, means he can go in fearless and unless all 3 go down he'll continue to do so.

Tank Triforce Ekko abused item and mastery synergies, and NOW, people want to keep on the mantle with Triforce Katarina.

Universally useful items hurt the balance of this game more than RITO's less than stellar design.

I name the Rengar rework a failure, complete utter failure, but maybe if he didn't got an acumulative 20% bonus damage from masteries alone, Maybe he'd be more balanced (unlikely, but meeeeeeeeh).