See, though, I don't have to worry about it too much. My guild hasn't failed a dungeon in months, in fact, we beat Arah path four last night with two guardians, an ele, an engineer, and a mesmer - an odd mix for a boss that requires heavy dps. We still beat it, though, because we were communicating with each other and adapting our strategies.
God bless those that play with pugs often, it must be infuriating. All is well in the land of Guildruns!