Everyone assumes Australia will be able to operate the LHDs as the Americans do. America routinely sends its warships out fully loaded with Marines and their air wings for long 6 months deployments. I doubt whether Australia can do the same.
More than likely the Australians will send their LHDs loaded with its Army personnel and equipment out for planned exercises involving amphibious landings. Outside any peacekeeping or humanitarian missions, the LHDs will be anchored in port waiting to be called upon. With only two in service, they don't have the number of LHDs the American navy has to deploy them for regular 6 months deployments, especially for sea control duties.
The Australians also don't have enough Army personnel to regularly deploy a battalion of men on these ships for long deployments either. Yes, their Army will be able to send a battalion of their rapid reaction forces to man an LHD or two for short humanitarian missions and for planned exercises, but not full time.
If the Australian make the mistake to use these LHDs full time as sea control ships, as light carriers, and acquire F-35Bs for them, they won't be available for the sealift missions they were designed for unless they are kept close to home. Sending them off as light carriers for a RIMPAC exercise off Hawaii is too far from home.
Yes, F-35Bs can be operated off the LHDs, but is the Australian Army's rapid reaction forces as large as Spain's, Italy's, France's, or the United Kingdom's? Even if the Australians bought a dozen or so, the squadron wouldn't be ready full time either. They would only be ready for a planned exercise or for short humanitarian missions.
These ships were bought for one purpose, to be ready to sealift an army battalion of their rapid reaction forces. Except for planned exercises, I suspect they will see most of their time anchored in port, waiting to be called upon for sealift when needed.