I'm experiencing this problem as well. It started about 3 weeks ago when during peak times I'd get crazy lag spikes from 4pm to 11pm GMT+8 (from the Philippines btw). There was one week where it got so bad, I was lagging even when it's non-peak hours. I thought it was my connection (my fiber connection weeps at 600ms+ I got) so I tried ADSL and LTE (different ISPs) but I was still lagging. Then I switched to my alts on NA servers (Excalibur and Adamantoise both on 160-240ms) and it was okay, I even considered transferring. I tried pinging other JP servers as well but it was only from Tonberry and Ramuh (which shares the same IP) that I was getting 600ms+.