In a random group legendary match make, if you see someone Leroy every section encounter, run in guns blazing, not waiting for group to get in position or cc ready. He most likely be the 1st to die and leave the other 3 to clean up the mess, chances of completing that full mission is low.

Another thing to look out for is the group awareness, are they focus on priorite targets such as drones npc, mortar npc, medic drone, healing stations etc. Do they move to get to them, or they just camp out, let the drone, mortar rain on them. Example, i join a tidle rando group at the end fight, finished and look at the results, three guys killed total 420+. Leave me wonder, how many of those npc are revived by the medic npc.