You do realise people 'leave and join' ( the same match about to start) games so they can be on the opposite team. This so so they can boost, often they will start out together and you will see them constantly leaving and joining until they are on opposite teams.
One group I followed for 3 games and ruined there experince, I finished at the top of the board, once. We lost the last match, but there individual score was woeful LOL. They finally left. I have video of those games, I set up a turret in there cheating area on Mirage and they still tried to cheat there, I racked up the kills 
But if you take your time and are patient you can usually identify these groups. If I recognise them to late, I stay and try to ruin there cheating. If I am facing a down hill battle with these cheaters, I leave.