I've now taken to booking a one way out of Oz and then booking 12 month returns out of Singapore (and each time having to book another return out of Singapore to ensure I am guaranteed on a flight back to Oz to make I can get back to work on time). I figured that even with the higher cost for a 12 month ticket, and the inevitable date change required once I worked out when I actually want to fly, it will still be cheaper than booking a return flight out of Oz.
Just realised that one pitfall of booking flights from outside Oz is that the trip won't be eligible for travel insurance under credit cards. Just checked my credit card terms and conditions and it firstly needs to be a return flight, and the outbound needs to be from Oz.
Ok, add on costs of separate travel insurance, but I think it'll STILL be cheaper overall than an ex-Oz flight...