Sorry but preseason doesn't really count as far as your peaks go since no one takes them seriously.
Either way, if snowballing is what you hate, then how about trying some champions that can defend against that? Judging from your match history, you play assassins almost exclusively which are THE most feast-or-famine type of champion by design. You're definitely setting yourself up to be at the mercy of a coinflip between who gets fed.
There's plenty of champions who are relatively* effective against hyper-fed enemies. Mages, hybrid champs that can build versatile, anyone with good CC.
Also, it's not easy to fix snowballing. Do you have any ideas on how YOU would do it without unfairly handicapping someone just because they're performing well?
*if a champ managed to get fed in the first place, the enemy team shouldn't usually be finding them easy to deal with.