Is my Graphic Card or PSU failing?

So I had recieved my now third RMA of the 780 Ti I bought from EVGA. The prior two cards, while running well, had constant temperature problems, whereby I would have to run the fan at 100% to keep it from exceeding 90c. In the initial month I recieved the third card it ran perfectly fine, temperatures ran fine, and there were no signs of artifacting or crashing. It wasn't untill roughly a week ago when the card started crashing in virtually every game I played (with the exception of less demanding games such as Borderlands 2). The card will work fine for the first 10 minutes or so, but from there on it starts to show several artifacts, inevitably ending with either a crash or freeze. I've made many attempts to fix this problem, from wiping my drivers and reinstalling, checking my computer for any viruses, modifying my fan curve, and even lowering the stock clockspeed of my card to -105 MHz, but none of these methods had worked.

So I talked to a representative at EVGA. In telling him all of my problems, he suggested that my PSU might be the culprit, as apparenly the 12V rail might be failing. So I had checked this in the BIOS, the voltage stays within the 12V range but does fluctuate quite often. It typically stays at 12.096 and every 30 seconds or so would jump to 12.192 for a second, then lower back to 12.092. This is a platinum rated Corsair AX860, so it would be my last assumption that my power supply was failing, especially considering my previous two cards, while running hot, did not show any artifacting or crashing whatsoever.

What do you guys think? Is it a faulty card? Or is my PSU failing?