Enforce a Code of Conduct
Why can't you duplicate the modes, Duos and Trios, but have an automated Code of Conduct? For example, if the player is inactive, standing still doing nothing for 5 minutes or more, they are kicked out and can't rejoin for 15 minutes. If they go too far away from their teammates they get a 'leaving game area' style message. This shouldn't be an issue if the player actively selected the suggested mode. Also, only players who were serious about playing as a team would join for fear of not being able to play for awhile.
I'm tired of playing ten or more matches with players who don't care if their teammates are with them or not, leave prematurely, or stand still for 15 minutes eventually getting killed by the boundary moving. I will leave for another game and take my money with me if something isn't done soon. I can't take another morning of the same things happening over and over again.