They're not making a AUS/NZ specific server (not now, anyway). They just redirect those who close to that region for the games (like DIII) so we'll have lower latency.

No news if this affects SEA players, but I noticed a difference in ping from 250 - 280 to now, which is about 210 - 230.

Australia is closer to us than US, therefore, if we get redirected there, less 'hops' of your connection is needed to make the needed informational transfers than you would usually have when you connect directly to US, as US is further from us.

Yes, we usually have to go through different gateways to get to US.