The single biggest problem I regularly see is a single teammate going out and getting themselves, thus everyone else, hurt or killed. It doesn’t seem to matter what difficulty this is on. Yes, sometimes the AI pulls a bastard move on us and wipes the lot. But I would rather that than someone doing the same by deciding they are going to go halfway back through the map to get a grim. Or race ahead to do the same. Or just wander off.
My suggestion; earn through consecutive successes the right to try either the existing higher difficulties or new tiers of whatever difficulty we succeed on which earn greater rewards.
Just a thought, but poor teamwork is the single reason I don’t play this more. So maybe there is a way to reward good teamwork without throwing idiots into the more difficult games.