Well like I said, the symptoms are consistent with overload of the graphics card, but not every crash is caused by the same thing. For example on my system, prior to the Catalyst 13.9 driver, (I was actually running the 13.10 beta driver I believe) it was crashing every so often, but it has only done a day it once since then. Both AMD and nVidia have released new non-beta drivers in the last week.
Another thing I'll mention, it's not really specific to FFXIV but it is to Overclocking. I had a PII-300 CPU that was OC'd to 450 and it worked perfectly for the longest time, and then Diablo II came out and, the game would BSOD after 5 minutes, every single time. After that, any video I played that used the Divx codec would also BSOD the computer. Turns out that the game was calling instructions that are only available on that CPU, and by all accounts, those (MMX) instructions tripped the BSOD. When I replaced the CPU with a PIII, all BSOD's went away. So in relation to your story, all I can suggest is that either you try the stock CPU/GPU settings, or you swap out the video card with a newer model just to eliminate one or the other as the problem.
FFXIV is very demanding of the CPU and GPU, so it wouldn't surprise me if some peoples hardware, is actually unable to deal with it.
