My 1080 FTW Hybrid I got on 8/26 has been having the same issue in World of Warcraft, mostly when gliding or on a flight path with max view distance maxed out. The EVGA Support were very professional & nice to me, I'm hoping to have my replacement in next week. It's nice how with the Advanced RMA I'll have no downtime, just have to reboot once a day or so from this through this week while waiting. I'll have to try the debug mode you guys are mentioning in the meanwhile.
Even if the newer cards are default boosting 100mhz less, I just hope my new one has no coilwhine & I've fallen in love with the Hybrid and how easy it was to just plug in & go. 35C at 2000mhz and being silent under full load what it's all about!