Perth has a terrible reputation in regard to Priority Luggage. Especially the ULD (container) loaded aircraft (763's, 747's, 330's) where they can blame the dispatching port. It seems to be a game with the handlers there ...
Every so often they get their act together but within a few months it's back to 'random' order.
Even CBR has it's problems, but at least there, a lot more attention is paid to ensure luggage is placed on the carousels in priority order ... Purple Business Tags first, Yellow and other priority next, then the remainder.
However, it's a bit easier there, as aside from the odd 763 from MEL (which is mainly freight anyway), 'tis all manually handled and Purple luggage is deliberately put on the conveyors first.