"balancing" has more to do with finances, than how broken champs are.
I'd bet my life.
Why nerf a champion that is selling hot? people will stop buying causing Riot to literally lose millions in champ and skin sales.
How secretive and vague they are about their reasons for making changes is evident enough.
Take Ahri for example, there has been thread after thread on how inaccurate their reasons for nerfing her charm were. Riot hasn't clarified it any. Simple explanation is that she isn't selling as much as some other midlaners she potentially counters. (just guessing there)
they are releasing a new champ soon. If Ahri - who doesn't sell hot - counters this new champ mid lane, it could potentially hurt that champs sells numbers.
preemptive nerf to Ahri would likely increase the sales of the new champ. Really no idea,
But i am certain they wont nerf a money maker.
its bad business. They are doing ALL of this to make money. Riot is not a charity.
Some people seem to forget that.