The LeaverBuster System Does Not Fix the Main Problem
If I get someone who afks in a game or is just gone from when the game starts, great! I can report them afterwards and be confident LeaverBuster will punish them. But that doesn't fix the main problem with afks, which is the horrible experience for the four players you leave behind.
Punishing repeated offenders will address this, sure, but there are players that LeaverBuster doesn't work on or shouldn't work on. Sometimes a guy just fails to connect because his internet goes out. No joke, a week ago I had someone connect to the game at 10 minutes and say that his girlfriend shut off his computer while he was in loading screen.
Sometimes this is a genuine computer or real life issue, not someone being a troll, and in that case they aren't going to be punished too harshly by the LeaverBuster system (because they don't regularly do this) but they are going to have just as bad an impact on the four other players in the game.
Please Riot, reduce the surrender time to 10 minutes. Yes, this will undoubtedly negatively affect normal 5v5 games, but it will overwhelmingly positively affect 4v5 games. Being forced to play a 4v5 for 20 minutes inspires rage and tilt and makes the next game go worse. We don't deserve this experience as players.