I think the solution is easier than that even.. They need an option to just Duty Finder with only people from your server. Yes you might have longer waits, but then your playing with your own community and plus you can just ban people that suck. I'm assuming the Duty Finder isn't going to pair you up with people on your blacklist -- problem solved. This creates more accountability of the player knowing if they screw the group over everyone is going to know and learn who the bad people are...