ISP: Nippon Telegraph & Telephone Corp (NTT) optic fiber
Location: Japan, Tokyo

I am having the exact same problems, pinged all sorts of JP servers with no packet loss while all NA servers have a 25% packet loss in 100 pings.
This rendered me unable to tank in dungeons and cannot progress the game further because of this.

Square enix needs to either respond here and give us an explanation or enable the server transfers.