So basically after playing a bunch of games I've noticed a lot of people tend to leave halfway though the game. Now although this is not as annoying is it would be in a team based game, it can still really get you down when your doing well and everyone leaves.
So I had an idea, basically implement a leaver system, much like the one in the popular game Heroes of Newerth. Essentially if you leave a game before you are eliminated you will get one "leave" added to your profile. After you get a certain amount of leaves you would not be able to play in a game that disallows leavers. In addition to this, you should only get 25% of the exp and crystals you would get for actually being eliminated and not be able to join another game for X amount of time.
Now although people could just make another account to get around this, it would at least discourage anyone who is serious about playing the game from leaving just because they are doing badly.
In Summery:
Person leaves game - looses 75% exp from that game and cant join another one for X minutes. Leaver count +1
Leaver count reaches Z number (perhaps % of total games played) - Player gets "leaver" status
Leaver status - Can not join games that do not allow leavers (much like games that don't allow guests)