Sunfish didn't you work at AN? They never delayed a passenger? 767s were grounded why?
Sh*t happens. The crew would have extended up to the point that they couldn't extend anymore. Some would have just got off as soon as the normal duty hours limit was up. The pax would have got off sooner though their chance of actually going would have been deminished. Which is the lesser evil? So it seems the crew went above to try and get the pax away even though late, this resulted in a longer stay on the aircraft than all would have liked.
Could the delay have been better handled by the company. Probably, though they have no control of the security requirments. Melb airport and customs and immigration have some role to play in this. QF possibly could have flown a crew down to MEL off standby if the crews were available and the called out crew would have been able stay within their own duty limits having been called out.
As for this tripe about depatching with known problem YGTFKM. It is a brand new jet!!!!! In service for two weeks. You would get on thinking it would be in perfect working order and any issue would easily solved, you would be unllikely to hold boarding if the issue appeared early. It would not have many MELs let alone any EAs or ATPs. This is a non-event though inconvincing for pax. Sad thing is that it is getting more coverage than Air berlin or AA overruns which are much much more dangerous events.