It's understandable why raiders and Antags quit. My team just survived a T1, R1 Doldren and it was a relatively low ranked team on a mission where the environment greatly benefited him/her. The minute I saw him, I proposed a quick surrender and ironically it was the two low ranks who decided to play. Myself and my team mate, also a T1 player were both going for rare BP's. We JUST scraped through, with myself managing to dish out the damage to the boss, while trying to avoid the Antag. Had the Antag just targeted me he probably would have won as I was knocking about 45% off the boss health bar every shot. It's not fun when a BP is on the line. Thank goodness we made it. Would have been even worse had been a last chance pot play.
But yes, stupid punishing players who quit because the enemy is way too strong for them. Put it this way, I played a mission, as an Antag Shae and hit all 4 players with a burst from Sa'Dhu. They all hit wounded state, one shot by enemy grunts, one killed by an elite heavy who took the aleph and used a super boost, chasing the remainind raider, whom he caught after I wounded him again, with a couple of well placed shots. Two players quit there and then.