I think what the Aussy Government is worried about is all the QE around the world, and its medium term effects on the Australian petro/mining/China based currency. They probably suspect in a soft world with lots of QE the Australian dollar may go up to 1.10, and that would make it uncompetitive and kill lots of investment and momentum from raping the land that started in the past few years.
Hence they lowered rates just a tiny bit to soften the currency via interest rates, and maybe boost the economy. These are all dull instruments.
The Chinese economy could pick up slightly after a lull for a few months, that could cause a temporary spike in raw material costs, whereby making the Aussy dollar appreciate to 103-105 again by June.
Hence the half percentage point drop is there to stabilize the currency in this range of 100-103 in my opinion.
I don't think Soros would dare short the currency, its much too risky, and given the Euro FXE is almost 132 today, its a better bet.