Becoming an expat

In Australia, you are taxed on your world income if you are deemed an Australian tax resident. If a tax resident leaves Australia, he is still regarded as an Australian tax resident, if he has not severed all links with Australia e.g. for example still owning a residence in Australia. As a rule-of-thumb, the ATO will often deem a person to be a tax resident for two years after he has left Australia. Citizenship is irrelevant for tax purposes.

I agree with all of that, apart from the rule of thumb you describe. The ATO states clearly that the first tax year you are out of the country for more than 6 months would be your first non-resident year.

My issue is whether he ATO is likely to still claim my tax residency despite this. I believe from replies to this question that they won't unless you return after not severing ties.

You  must, first of all,, ascertain your tax residency before leaving Australia. If you are an Australian tax resident and you clearly show an intention of returning to Australia within say a year or two and you still have strong ties to Australia e.g. continuing to own a residence, maintaining Australian bank accounts etc, then you are likely to be deemed an Australian tax resident even though you are living abroad.
You should seek competent Australian tax advice.

That part I know. Thanks, though.