I've been saying for a couple years now that the best way to bring snowballing in line is to reduce kill gold. I'm thinking by about 60% but I'm open to arguments for different percentages.
The idea is to reward skill. If you're the more skilled player in a lane, you would kill your opponent over and over again regardless but if someone gets fed off a noobshit feeder and you are more skilled, it would allow some breathing room for you to impact the game and halt their rampage before they start 1v5ing.
Just yesterday, I had a game where we invaded, fucked up and the enemy mid Irelia got a tripple kill. After that, all she did was roam around the map killing everything at will until they won. Nothing and no one even had a chance to stop her. Was it because she was skilled? No. Anyone can be Faker with a massive gold lead. An accident enabled her to carry so hard, not skill. This is the fundamental problem with this game.