I've noticed I also get similar packet loss issues with Umontreal.ca (funnily enough, same city as my server). If it's not optus, then my guess is that would have to be where it routes to is the issue (still an issue with optus imo). Friend of mine in brissy and another in Townsville is with Internode and both have zero problems with the same server I'm connected to (jenova).

Oh and since patch 3.3 I now get error code 90006 and can't play longer than 5-10mins before getting d/c'd.