Since Heavensward, FFXIV does not support Eyefinity.

According to the AMD website, FFXIV has "Gold" certification standard. This is posted on the AMD website: http://support.amd.com/en-us/recomme...ftware#k=#s=81

About 3/4 of the way down it says very clearly:

Final Fantasy XIV Online RPG Gold

Please enable Eyefinity support as per the FFXIV stated certification.