I had an issue with a intermittent flicker that happened during larger page renders on my Ubuntu box when using FireFox browser. I updated drivers but could not fix issue. It turned out for me that when installing the video card it was placed in the second PCIe X16 slot on the Asus Z97 pro board. This caused the issue, all video functions worked using the second slot as my single video card slot but there was that flicker. I moved the card to the first slot and my system started to work great. Just a heads up to use the first slot when building out that board.
Flicker Issue with Firefox on new custom built Asus motherboard comuter