That will depend on which city you are coming from. HKG would actually be the best option but then it will depend on the connect time.
Also Eastbound in the winter with some of the huge Jetstreams around it could almost be quicker through Perth.
They'd want to pick up their game dramatically, its more than just transit times that count, both Emirates and SIA's A380's to LHR from Sydney have more legroom and wifi.
QF have said they are configuring their 787's for extra long haul flying. It will be interesting to see what kind of seat pitch they put into economy however the transfer back into domestic economy on the inbound leg might be a bit painful.