I recently got an MSI R9 390. Before this I had an Asus GTX770. Both of the cards were factory overclocked by the OEM. Nothing else in my setup changed; my processor is a mildly overclocked i5 4690k running at 4.2GHz (which has proven itself completely stable over a year of usage with the 770), and for RAM I have 16GiB of Corsair's DDR3, which isn't overclocked per se but is running on the manufacturer's XMP settings of 1866MHz.

With the 770 everything ran just fine and dandy and I had no crashes whatsoever in DX11 no matter what I did, and the game also ran well in borderless fullscreen. However, with the 390 I've been having a fair bit of GPU driver crashes at seemingly random times while using DX11, as well as having awful microstuttering in borderless fullscreen in both DX9 and DX11.

I've been playing lots of MGS5 lately and it has ran just fine on the 390, but haven't really tried any other games on it yet.

I figured the FF14 crashes might be because of the overclocks actually being unstable, like that one guy in this thread repeatedly mentions, so I underclocked it down from the 1040MHz factory overclock down to the reference clock speed of 1000MHz. Didn't touch voltages. I wasn't particularly surprised when the crash happened exactly like it did before.

During this time I played just fine for about 40 minutes. Did an Expert roulette, and teleported around a bit doing random stuff. I only alt-tabbed away from the game two times during this time, to check a Steam message I'd gotten.

Then I figured it's high time to trigger the crash, and alt-tabbed to Firefox (which has hardware acceleration enabled), scrolled around on a couple of webpages, and then tabbed back to the game which promptly crashed within ten seconds of regaining focus.

As such, I'm inclined to believe that at least in my case the crashes are caused by other programs using hardware acceleration alongside FFXIV. They seem to always happen right after I alt-tab out of the game to my browser. I don't really want to disable hardware acceleration in literally everything, so I'm just going to play using the DX9 client for now.

This doesn't happen in the one other game that I've been playing recently, MGS5. It also uses DX11 and is a 64-bit executable, but even if I tab out of it to do some web browsing and stuff it won't crash.