I presume you're playing on a US/EU server which would explain your high latency. Ironically enough, the JP servers are physically closer to Australia/New Zealand - I have characters on both server groups, and I find my characters on Ridill (JP) have less lag than my Balmung (US) characters.

In particular, Tonberry has apparently the largest English-speaking population on the JP servers, as most of those players are Australian/New Zealand/Oceanic. So maybe transferring to a JP server like Tonberry may help.