It is unavoidable that international flights are delayed upline due to late inbound aircraft, but this also happens to originating flights in SYD.
This seems to indicate that resources are being stretched to maximum leaving nothing to cover these circumstances.
Eg QF5 sat 6 dec delayed from 1700 to 2100 due to operating aircraft delayed ex CDG.
Now this delay occured 24 hours prior but still another aircraft was unable to be found to cover this flight.