I may defer to others more versed in Australian investing and cost systems. Partially unfamiliar, though have been reading other cases with interest and informally studying long term international investment performance (stocks, real estate, bonds).
It's unclear to me whether the "standard" 4% rule of thumb is useful in a real estate heavy allocation like you have. If it were, and the debt structure did not interfere, your 1.5M $AUS portfolio would presumably enable spending of $40,000 $AUS/year less taxes (not familiar with Aussie tax). Taking your $24k spend rate at face value, I presume that FIRE would be plausible.
But I second lhamo's concerns. As an outsider, it seems that returns on the real estate are lower than the "standard" rule of thumb. To me this also implies that there could be a bubble in this asset. There are markets in the US with similar pricing, but most Mustachian landlords avoid owning in them like the plague. Debt presumably increases any risk inherent in the asset class.
For what it's worth, landlords in America frequently have expenses (not principal, not interest - operating expenses, including vacancy costs, capital expenditure, maintenance, tax, property managment, etc) close to 50% of rent. Not all landlords recognize all the expenses until they occur in large surprising lumps. Your expected expenses are far lower than this 50%. Is that consistent with long term complete expense standards in your market?
lhamo addressed this, but - your stated rent less expenses and mortgage interest produces $10,000 per year against stated equity of $880,000. That's a return of less than 1.2% per annum even if your expense estimates are correct. Is that the best return you can find? Are we missing something here?
Supposing that the $10,000 per year is the best option, what is the expected return per year on the other main assets - the $200k of cash, $170k of stocks and the $200k of superannuation? Is the expected return in total less than 24k?
If the cash gets eaten by rental expense variations and vacancy, could you be forced to sell your crown jewel properties at discounted prices in some market downturn?