If you haven't done so yet, give your route a good look. Chances are, there are problems in route from your localized network to SE's ISP--we see a lot of peering issues these days. Your ISP determines who that third party peer is, so they would be the better choice for investigating and addressing such issues if found.
If running a trace route to your lobby server (tracert neolobby002.ffxiv.com) shows big spikes along the way, that is indicating there may be elevated congestion on/around that segment of your route. Providing that tracert report to your ISP's Tier3 Support team can go a long way to addressing the problem. If you can also improve things by using a VPN (can use the free trial periods for testing), you can further demonstrate to them that it is a routing issue for them to investigate (basically that is what the VPN's do--alter how you are routed).
More often than not, this is an issue that your ISP can and should be addressing for you.
