I tried forwarding 54992 to 55551, no change.
I'm currently in Japan (Plala/NTT/200meg fiber) and connecting to a US server (Cactuar).
Some interesting things I've noted:
1. The login servers seem to be only in Japan (124.150.158.117, 124.150.157.190, 124.150.157.126). Regardless of whether I connect directly from here or VPN from the states it's the same.
2. 199.91.189.24 is unplayable. Constant lag spikes, disconnects.
3. Used a VPN to put me in California and connect to 199.91.189.74. Game works no problem now.
4. Disconnected VPN, and connected to Cactuar again. Was put back on 199.97.189.24. Back to same problems as before.
Some conclusions I got from this...
1. Certain servers - not to be confused with worlds - are having serious issues.
2. When you first login from a region it assigns you a specific server and has memory of that.
3.When you login from a different region is assigns you a new server.
4. I have several friends locally who also play on Cactuar. Some are fine and some have the exact same issue. I haven't had the ability to confirm, but there's a good chance that there's several possible servers per region, and only some are having issues.