To many software/applications, the Intel HD/nVidia Optimus is to be seen as one GPU (Intel HD); But you can configure so that applications will be instructed to utilise the preferred GPU.

Go to nVidia Control Panel, 3D Settings > Manage 3D settings > Global Settings (tab) and change the "Preferred graphics processor" to "High-performance NVIDIA processor". Or if you prefer finer tuning, then use "Program Settings" and add the program to customise, for FFXIV, you must choose "FFXIV.exe" (alternatively, you can select the program folder by using "Browse").