If you guys haven't figured it out yet... this game is very CPU intensive.
Example. My wifes old comp got a 4k score on Benchmark. I upgraded the GPU to a 4gb 760GTX card. The benchmark went up to 4800.
I took same card and upgraded the CPU to a i7-4770 and her score went up to over 13000.
All scores reflect 1920x1080 on Max. No graphics card tweaks or game tweaks.

So short story is, getting a better GPU will not help you as much as you think with FFXIV. You need good CPU and GPU.