A clear is a clear. Why does it matter if a group could kill something faster if they had X job instead of Y?
Hell, let's go a little further and say a group could kill a boss faster without Casters at all. DRG, MNK, NIN and BRD. BLM's and SMN's are irrelevant as neither have debuffs that benefit other DPS (Disembowel, Dragon Kick, Dancing Edge).