the xONEx fares are based on where you start flying on that ticket. Theoretically the cost should be the same independently of the issuing airline, but each has different policies on the application of "taxes/airline fees" for each flight segment. Typically the airline flying the first segment or first international segment would be the ticketing airline. But many (AA/QR) will likely be willing to ticket if they market one of the longer intercontinental segments.
An inexpensive ticket to Colombo (CMB) to start would at current exchange rates reduce the base ticket DONE6 cost to AUD 11538 and permit you to have more stopovers in the South Pacific region.

Happy wandering
Fred