FFXIV can run a very slow speed and be perfectly playable. When I was in Barcelona I played this no problem on a wifi that was on 30% pick-up, and the wifi itself was beyond crap. As long as it's steady you'll be fine, trust me.

EDIT: The reason why I said for it to be steady is because if you are running a dungeon for instance you'll suffer lagspikes or dc, but doing things solo it doesn't really matter at all, it'll just be a nuisance.