For some reason I keep forgetting that Dead Can Dance are Australian. Perhaps because they don't receive as much attention as Silverchair in the mainstream press, but anyway.
There's not that much good Australian metal, diSEMBOWELMENT is quite good, but I believe they've broken up, Nazxul are decent black metal but nothing revolutionary, Reverand Kriss Hades' of Nazxul has his own solo ambient/black metal project worth checking out, Psycroptic are OK, I saw them live and was very impressed, but typical grindcore/death metal.
Avoid The Amenta like AIDS, they were pretty popular a few years ago, heard the album, was average, saw them live, was dreadful.
Hm, that's about it, there's a reason why Australia is considered a cultural wasteland.