What Aussie ATC's & ASA Managers think is busy may not be busy for those experienced internationally. Comparing Perth ATC to Hong Kong ATC may not be realistic.
Having said that Aussie ATC's are constrained by some ridiculously pedantic (an*l) "rules". They have to spend a lot of mental effort covering their bums instead of working traffic. But I guess that is what ASA Management think is "World's Best Practice" or whatever lame cliche they are throwing around these days.