The system seems to match you against opponents based on your performance on your best/main chars, even if just playing quick play. So either you end up being a useless carry because you might be playing against 3k rated players and maybe you play the char you are practicing on at 2k, or you end up being 'that guy' that picks Hanzo and everyone blames for making the team lose. The only time it seems to work out is when you have one of those teams with no tanks or healers where there is no team synergy at all, in which case you just get completely destroyed by a pug team with any amount of coordination.