The developers haven't even submitted the game for classification in Australia - therefore they are merely making assumptions about whether or not they have to edit certain content. This is a classic case of paranoid self censorship. Games such as Gears of War 1/2, Dead Rising, Saints Row 1/2, God of War 1/2, Dead Space, Bioshock, UT3, FEAR 2 etc have all been released in Australia uncut. The last time this happened the assumptions turned out to be unfounded - GTA IV was edited by Rockstar originally because they thought the uncut version would be banned, but they submitted the uncut version for classification when they released the PC version and it passed without any edits.
All that will happen is people will download the uncut version, whether the CB censors it or if Blizzard self censors it. This is a case of the developers being unwilling to try to get the uncut version classified. It is THEIR decision, not the Classification Boards.
If the uncut version were submitted for classification in Australia it would most likely be passed. Contrary to popular belief most adult games don't actually get censored - the sensationalistic media just LOVE perpetuating complete BS. The system in Australia has a lot of problems, it does indeed need an R rating but there is no way Diablo III would be banned. It's just the developers being paranoid.