normally you can find the errant mook, its normaly a non stealth unit stuck up on a wall and you need to look up high to find it, similar problems used to happen from time to time with reactor map in me3 the biggest problem for me is the ranged killers are normally the first to ditch the match instead of looking about and it happens a lot if the host is suffering from lag spikes, something that happens a lot if your on the outer edges of each others play regions, or they happen to be on older internet connections, of course if your a party of level 1 lego's your knackered since none of you can aoe or taunt or use a ranged attack .... which just made it an annoying waste of 5 minutes back when you could host migrate but now with migrations failing so often its more like a waste of 20 minutes /
still the game is fun enough even with its oddities and occasional bugs, some of which can be fun and work in your favour (random one shot kill on boss mobs when attacked form the right angle for instance) so like everything you take the rough with the smooth 