I've done more testing and I get less ping on other servers. I get around 260 ping in the EU and around 300 in the US. Re-installed the game and restarted my router, still 400-500 ping on Au server.
If it's only you then problem obviously is on your side. Maybe talk with your ISP.
And what intranet connection you have? You sure that nobody else is using internet while you are playing?
If someone is downloading something, or watching movies online, then it can affect your ping (but it depends from internet speeds up/down).