My solution to afk/dc in game. Join in progress que.
Im going to start with 2 facts: You are at a severe disadvantage down a player. Even if a DC'd player comes back after resolving their issue, it is likely they cannot recover for the lost time.
I think that the game should replace the DC'd player and put a new summoner in control of their character. The new player would que specifically to join in progress games, and would not receive ladder points but would get a fair bonus in IP for helping out. The DC'd player would be barred from reentering after they've been replaced but can spectate the game or be locked out from playing for a time.
It would be hard for riot to do this i am sure but it would go a long way lessing the impact of disconnects on everyone's League experience.