Well... between FFXI and LOTRO, i have to admit that I never had DCd so frequently. In fact... I don't think I ever DCd with LOTRO.
Default install of ffxiv client and router. No tweaks to ports required.
After swapping out my linksys wrt54g2 for this NETGEAR WNDR37AV (gaming) router my packet loss dropped from 2% to 0. I really think the issue is the quality of your router/gateway/modem.
I write client/server socket applications from time to time and if you don't handle these sorts of issues manually... software craps out. It appears that the client/server doesn't have any real tolerance for packet loss.