Aside from a questionable "benchmark" that may not even produce valid results, you have nothing showing any sort of issue exists. As you can see in this thread http://forums.guru3d.com/showthread.php?t=396064 the only "evidence" posted at any point, is YouTube videos claiming to be running GTX970 and experiencing stuttering and hitching every time VRAM usage exceeds 3.5GB. So, if you say the video posted by Spets is unacceptable, every shred of "evidence" posted on this supposed "issue" is also unacceptable for the aforementioned reasons. They're YouTube videos that could easily be faked. So, now it's down just to our experiences and a statement from NVidia. In your case it could have simply been a faulty card from the start.