If your fireteam was any good, you would have carried that 309 through hard mode with no wipes (ok 1 wipe max). Your behavior was elitist. Light level has nothing to with skill. It DOES have a little bit to do with experience. But all things being equal, the lowest light level character is more likely to die first, because he takes more damage and deals less damage than the other players. That's obviously the weakest link. But that's not necessarily an issue of skill. If anything it's an issue of experience, or your fireteam is not delegating tasks appropriately.