To be honest the leaver penalty doesnt even really work. Not once have i left a match volentarily nor have i personally disconected from a match. However, i have recieved multiple penalities after the "looking for players" screen doesnt find any players and sends me back to the title screen.
I have never come across a game where the afks and leavers are so numerous. 1 game in 10? fine. it sucks but it happens. 1 in every 2? thats a problem. I honestly dont know what i would do to combat this. Increasing the penalty is an option but if the penalty system isnt working properly it will result in unfair assessments.
Another possible solution would be to implement computer players in place of leavers. It definitely wouldnt be perfect but it might just be better than having to wait for a fourth player.