That's a good spot. You can pretty much ignore the Servitors, but Captains, Stealth Vandals and Shanks will make their way over to as far as they can walk, so you need to keep taking them out. We kept one guy with Fireborn on the top at all times, there was one time where the other two were dead down there and a Captaian oneshotted me on top and we were saved only by my Fireborn. There were 3 times when my friends were both down and I had to make a run for it. I made quick revives, ran all the way to the left luring the enemies there and then jumped back over them and got back to the safe ledge. Leave shanks for someone with Solar sniper as they drop in one shot. The guy on ledge should warn about stealth vandals as he will be able to detect them the best. Captains are the hardest as you cannot one-shot them with sniper or fusion and they hurt a lot, try to engage them all at once so they cannot regenerate their shields. You need good arc damage weapons. Snipers may even be more efficient than rocket launchers, combine both for best ammo economy. Try not to waste elemental ammo on minions. Bring LOTS of sythesis for special and heavy, 10 each is not too much!