I have the same issue here. First few days I was playing it was fine. Lately its every few hours. Minus the occasional every 5 minutes. For what I have its as follows:
ISP:Oceanic Time Warner Cable - Speeds = 300MB download/25 MB upload
Direct Connected to Modem
Playing on Windows 7 PC - Not using Steam to run or update
Modem = Brand New
Cat 6 Cable = Brand New
Firewall settings are fine for FFXIV
Ping time in MS is 44MS average, 48MS Highest
Server: Adamantoise

Just to throw my hat in. I have been running packet captures on the connection with just FFXIV and Wireshark running. The issue is not with my computer sending data. Its receiving from the server. Server response after getting my packets will re-transmit quiet often. I have played many MMOs and other games via Steam and some non Steam games. This is the only one I have an issue with.