I'm running into so many situations of MIA teammates.  If they are willfully leaving a match or being disconnected (most likely given how spotty P2P servers are) I have no way of knowing.  What I do know is it severely impacts the difficulty balance of the match. 

Nothing is more gut-wrenchingly frustrating like having a decently leveled team get cut in half, with a Antagonist still roaming around with enemies that haven't been adjusted accordingly.  This problem only becomes more exaggerated when there's a MMR disparity between Antagonist and your team, causing the AI to get pumped up full of steroids.

My suggestion is the AI difficulty changes depending on how many are connected, or if that's too difficult increase the amount of rewards allocated at the end of a match.  It's unbelievable how broken this system is!  Stop working on skins and guns and fix the fundamentals first.