Champion strength/weakness and average game length, issues and questions.

So first off, does anyone have a place that offers good data on what the average game length is? Like i want to complain about X champion being weak or Y champion being too strong. But i also want to avoid bias that comes from only using my personal games to judge. Personally i feel like most games i see that aren't part of some big tournament, end by the 30 min mark. With a fair chunk of them ending around the 20-25 min mark. It's not all games but i'd say like 85% of them. Which makes me really want to ask for either nerfs to early game champions or buffs to late game ones. I'm getting kind of tired of playing champions who wreck face in long games, but are painfully bad in short ones.

With all that said, can we PLEASE buff Sona's early game? I know her late game is INSANE with her item synergies, off the charts CDR, and the fact that most people build her with lots of AP. But her early game is just SO WEAK, you don't have CC to set up kills for your allies, you don't have damage to pressure lane, you don't have meaningful healing/support skills, to top it off you are slow and made of paper/glass. I wish i could find data on what her win rate was in the 15-20 min braket, because i'm pretty sure its lower then 30% and that she was at least in part the reason her team gave up.