Looks like for the most part Metrocast funnels things through GMP TV, and then that goes to either Cogent or NTT. Not the greatest peering arrangement if I'm looking at the same company.

Sounds like you may need to get your ISP involved to take a closer look at what is going on along your path to the servers. If you aren't comfortable doing the traces and such, they should be able to do some testing of their own if they have a valid address to use. Since you are on Aether, they should be able to use either the DNS name or the actual IP address for the lobby service:

neolobby02.ffxiv.com or 199.91.189.74