ffxiv_dx11.exe crashes

[Weisshorn]

My GPU is not overclocked (i think), there is any means to check it ? And it's feels strange to underclock my hardware for FFXIV runs "smoothly", but still trying anything to solve it, it's playable but annoying =/

update I give up, i tried everything and there is no apparent solution or official help. Ty Darkstride and fulululu for your help.