This really touches on one of the biggest issues of PC hardware today: It is now so advanced that the general public cannot distinguish it from magic. You can talk all day about rendering theory, and how one generations ROPs stack up against the next. GCN vs CUDA cores. Whatever. At the end of the day the tricks in the architecture to get these cards to do amazing things really does not matter. What matters is the performance that these cards provide under a given workload. Given that perspective, the 970 is still one of the top cards on the market. Yes, it would be better if the card was better... but that is why there are higher-end cards. The Titan lineup, the Quadro lineup, even the 980. Those are the no-compromise high-end cards, and the x70 series of cards have always been right on that boarder of the upper midrange offering a few compromises to dramatically lower the price while still offering lots of performance.
In other words the 970 is no hellcat. The 970 is what would happen if they took a hellcat engine and body style, but then paired it with a slightly less capable drive train. It does not shift gears quite as nice, and it does not make quite as much noise off the line, but it is still a nice car and costs 25% less than owning a 'real' hellcat.
If nVidia was optomising for benchmarks that end up not reflecting real-world performance (as happens in the mobile markets and browser markets) then there could be a case to be made at a cover-up. If they were paying people to boost reported GPU numbers in reviews then that would be an issue. But saying that a card has 2960 whose-its paired with 9064 whats-its and it comes out that it really only has 2600 whose-its paired with 8750 whats-its after the hard has already been through a lot of unbiased testing and reviewing is not a coverup, that is just standard practice marketing because the whose-its and whats-its are things that are not comparable to any other thing in the real world. What you CAN compare are benchmarks, and the benchmarks say that the card is good under most circumstances, but that the card chokes under heavy vRAM usage compared to it's bigger brother, and so people should make their purchases accordingly.