When investment in Australia was very high and rising, and investment elsewhere in the world was very weak and falling, it was not surprising that the Australian dollar was at quite a high level. This was a textbook response to an investment boom.
But the textbook would also predict that as the mining investment boom in Australia unwinds and, hopefully, investment in the developed economies picks up, some realignment of the relative value of the Australian dollar would occur. This process has started, although it has been interrupted recently, partly due to the changed outlook for US monetary policy.