Only the person who leaves a Shuffle should have their MMR/CR altered

Am I wrong? Let's say you're in a lobby where one DPS is more than likely going to go 0-6, but all the rounds you play with him he stays in, then just as you're about to have a chance to fight him, he leaves and u lose a bunch of CR and MMR.

Wouldn't it better to punish only the guy that leaves? I know that someone wouldn't get their ''won'' rounds that way, but its a lesser evil imo.

Idk if this discussion's been had before.