These are all on a URL forward from your name registrar or a forward from your web host?
Is this a direct forwarding or are you using the same page but changed titlebars and meta tags and still shoiwng the original domain name and extension?
Or maybe a single unique splash page with links direct to the .com.au?
Insofar as I am aware I do not believe there is any SEO benefit having a registrar forwarded domain name. Certainly the search engines like these for cleanliness however I don't believe there is an SEO advantage or extra kudos.
my traffic rating has gone up 500-600% in the last 4 weeks
This could easily be bot activity if your traffic levels are not that high.