You're probably affected by the Level3/Ormuco routing clusterf**k. Go to arrstatus.com, find out the IP address of your server, open Windows command line (Run > cmd), and typ tracert followed by the IP address of your server. Post the results here.

Basically, the companies who own and operate the network infrastructure between you and SE's servers in Montreal are doing a terrible job of managing FFXIV's traffic, and SE themselves have no real control or say in the matter.

Many people seem to be able to get around these broken Internet routes by using VPNs like WTFast and Mudfish.