We got nothing for completing it except some added e-peen. Yes, we had range enabled, no we didn't have anyone on our team using bows/arrows. Everyone was in transitional armor or up (ranged sucks in anything more than leather). I can't count the number of times I got oneshot at full health by a Vitez or Sexy wielding an arbalest
Also, the reason you don't see the bosses was because the initial wave of them were dead. Only a couple were left and if you pause as I'm going down or through the door you can see some of the boss corpses (maybe)