you may be having high delays or packet loss along the route to the patch server. Might see some timeouts or very erratic response times if you run some tracerts or long ping sessions to one of them:

patch-gamever.ffxiv.com (should resolve to 124.150.157.126)

If there are issues either resolving the IP address for that DNS name, or you are unable to maintain a consistent path and response time to the patch server, may be time to contact your ISP and forward them the results of the tests via an email. Until they can address such stability issues, you may have to try to grab the download during off-peak times for the region where it's failing (like if it's a hop in Chicago, want to avoid their prime time). Otherwise, you could poke around some of the partner site forums to see if they've posted a recent off-line download or torrent link.