Played hours and hours with dx9 and didn't have a single crash. Switched back to dx11 and game crashed in Western Coerthas Highlands after 40 minutes of playing.

Faulting application name: ffxiv_dx11.exe, version: 1.0.0.0, time stamp: 0x55806a61
Faulting module name: ffxiv_dx11.exe, version: 1.0.0.0, time stamp: 0x55806a61
Exception code: 0xc0000005
Fault offset: 0x0000000000145861
Faulting process id: 0x16ac
Faulting application start time: 0x01d0aacfbcbf1fd6
Faulting application path: C:\Program Files (x86)\SquareEnix\FINAL FANTASY XIV - A Realm Reborn\game\ffxiv_dx11.exe
Faulting module path: C:\Program Files (x86)\SquareEnix\FINAL FANTASY XIV - A Realm Reborn\game\ffxiv_dx11.exe
Report Id: 85ca015c-16d2-11e5-8264-f0795965f776