I'm a "runner." I'm there to grind out my 100 marks as fast as possible and get my guaranteed engram at the end. I discovered that once I got to L27 or so it didn't really matter whether the other 2 players were there or not, so I go ahead, skip everything that doesn't need to be killed, and focus on downing the mini-bosses and clearing to the final boss in short order. If they catch up, that's fine. If not, whatever. They'll get the rewards at the end too no matter what they do during the run.