See the problem with Voice Actors tryign to do any kind of 'Australian' Accent is not where the accent comes from, but more the grammar and pronouncation behind it. Miranda from Mass Effect 2 comes close, but most 'Aussie' characters in games speak slower and clearer than a real life Aussie, due to pooftah American Dev/Pub teams making us slow down for the dumbass Americans who can't understand anything that isn't American, fake Russian or fake British.
We don't tend to open our mouths much (Lets the flies in!), we speak as quick as possible and shorten EVERYTHING! We also tend to roll words together with the talking quickly thing. I tell you this from personal experience, as I am a Queenslander with an 'Ocker' accent, similar but not as bogan or twangy as Crocodile Dundee. I've recently moved to the mid-north coast of New South Wales, to Coffs Harbour and all the local NSW-men are always telling me to slow down or repeat stuff.
If anyone wan's ta test me theory above, PM me for me skype address and I'll have a quick chat with ya about me accent an how I talk ta yous, eh? And far tha record, not all Queeslander's are 'bogan', 4.5 Million people live in tha Brisbane city dominated South-East Corner, and tha remaining 1.5 Million live in tha rest of tha state. Tha's right! We've even got CITIES in AUSTRAYA!