Yeah as Karishin said, this sounds like your card is overheating. So you may want to obtain some temperature monitoring software to see how hot your card is getting. With your specs and for the score you are getting it does sound like your system is overclocked, so this will increase the heat that is being given out as Final Fantasy XIV is also very CPU & GPU heavy.

So there is no game fix that will stop this from happening, unless you lower the settings of the game itself.

Sorry for the bad news.