I don't think the surprise is that the jet is performance limited, Joker. As you say, most jets are limited at or approaching their MTOW.
The surprise(or lack thereof) comes from the fact that QF management oversaw the acquisition of another jet that is not entirely suited to the task employed.
If they haven't considered a 30+ degree day with 5kts tail and OEI, then they have not done their job properly and should be held accountable.