Pretty sure an A380 scheduled DXB-SYD with planned fuel for the trip but then making an unscheduled tech stop in PER isn't going to need to dump a drop of fuel.
It would almost certainly have been above MLW on arrival in Perth..
The average Landing weight on a DXB-SYD is about 365-365T and with a fairly ordinary forecast for Sydney this morning the additional fuel would have taken that comfortably 370+. MLW is 391T, so with 3 or 4 hours to run it would have been about 400T at least....However Airbus allow landings above MLW in certain circumstances provided there's enough runway. This would qualify.