Not sure where you guys get your numbers, kyle from newegg tested these cards two days ago and the 970 was winning at 1080 by a fair margin in most games he tested while the 390 was only catching up at 4k (of course expected with the larger frame buffer, but really how many people own a 4k monitor):
https://www.youtube.com/watch?v=Q-N337-y7vI
And you have to include WoW in this, this is a WoW forum lol. Techpowerup is the only site i know of that still includes WoW benchmarks, the latest GPU review they did was for a 980ti matrix but it shows the 970 hanging with a 390x (sometimes beating it) which has a ~100 dollar price premium over it:
http://www.techpowerup.com/reviews/A...Matrix/20.html
Listen i get you all are banking on dx12, but there are reasons to suggest the 970 over the 390. Mainly gameworks titles and MMO's, and to a lesser extent people who want a fairly substantially lower power bill.