Well I figured I'd create an account in order to explain away what you're all seeing in the Ashes of the Singularity DX12 Benchmarks. I won't divulge too much of my background information but suffice to say that I'm an old veteran who used to go by the handle ElMoIsEviL.
First off nVidia is posting their true DirectX12 performance figures in these tests. Ashes of the Singularity is all about Parallelism and that's an area, that although Maxwell 2 does better than previous nVIDIA architectures, it is still inferior in this department when compared to the likes of AMDs GCN 1.1/1.2 architectures. Here's why...
Maxwell's Asychronous Thread Warp can queue up 31 Compute tasks and 1 Graphic task. Now compare this with AMD GCN 1.1/1.2 which is composed of 8 Asynchronous Compute Engines each able to queue 8 Compute tasks for a total of 64 coupled with 1 Graphic task by the Graphic Command Processor. See bellow:
Each ACE can also apply certain Post Processing Effects without incurring much of a performance penalty. This feature is heavily used for Lighting in Ashes of the Singularity. Think of all of the simultaneous light sources firing off as each unit in the game fires a shot or the various explosions which ensue as examples.
This means that AMDs GCN 1.1/1.2 is best adapted at handling the increase in Draw Calls now being made by the Multi-Core CPU under Direct X 12.
Therefore in game titles which rely heavily on Parallelism, likely most DirectX 12 titles, AMD GCN 1.1/1.2 should do very well provided they do not hit a Geometry or Rasterizer Operator bottleneck before nVIDIA hits their Draw Call/Parallelism bottleneck. The picture bellow highlights the Draw Call/Parallelism superioty of GCN 1.1/1.2 over Maxwell 2:
A more efficient queueing of workloads, through better thread Parallelism, also enables the R9 290x to come closer to its theoretical Compute figures which just happen to be ever so shy from those of the GTX 980 Ti (5.8 TFlops vs 6.1 TFlops respectively) as seen bellow:
What you will notice is that Ashes of the Singularity is also quite hard on the Rasterizer Operators highlighting a rather peculiar behavior. That behavior is that an R9 290x, with its 64 Rops, ends up performing near the same as a Fury-X, also with 64 Rops. A great way of picturing this in action is from the Graph bellow (courtesy of Beyond3D):
As for the folks claiming a conspiracy theory, not in the least. The reason AMDs DX11 performance is so poor under Ashes of the Singularity is because AMD literally did zero optimizations for the path. AMD is clearly looking on selling Asynchronous Shading as a feature to developers because their architecture is well suited for the task. It doesn't hurt that it also costs less in terms of Research and Development of drivers. Asynchronous Shading allows GCN to hit near full efficiency without even requiring any driver work whatsoever.
nVIDIA, on the other hand, does much better at Serial scheduling of work loads (when you consider that anything prior to Maxwell 2 is limited to Serial Scheduling rather than Parallel Scheduling). DirectX 11 is suited for Serial Scheduling therefore naturally nVIDIA has an advantage under DirectX 11. In this graph, provided by Anandtech, you have the correct figures for nVIDIAs architectures (from Kepler to Maxwell 2) though the figures for GCN are incorrect (they did not multiply the number of Asynchronous Compute Engines by 8):
People wondering why Nvidia is doing a bit better in DX11 than DX12. That's because Nvidia optimized their DX11 path in their drivers for Ashes of the Singularity. With DX12 there are no tangible driver optimizations because the Game Engine speaks almost directly to the Graphics Hardware. So none were made. Nvidia is at the mercy of the programmers talents as well as their own Maxwell architectures thread parallelism performance under DX12. The Devellopers programmed for thread parallelism in Ashes of the Singularity in order to be able to better draw all those objects on the screen. Therefore what were seeing with the Nvidia numbers is the Nvidia draw call bottleneck showing up under DX12. Nvidia works around this with its own optimizations in DX11 by prioritizing workloads and replacing shaders. Yes, the nVIDIA driver contains a compiler which re-compiles and replaces shaders which are not fine tuned to their architecture on a per game basis. NVidia's driver is also Multi-Threaded, making use of the idling CPU cores in order to recompile/replace shaders. The work nVIDIA does in software, under DX11, is the work AMD do in Hardware, under DX12, with their Asynchronous Compute Engines.
But what about poor AMD DX11 performance? Simple. AMDs GCN 1.1/1.2 architecture is suited towards Parallelism. It requires the CPU to feed the graphics card work. This creates a CPU bottleneck, on AMD hardware, under DX11 and low resolutions (say 1080p and even 1600p for Fury-X), as DX11 is limited to 1-2 cores for the Graphics pipeline (which also needs to take care of AI, Physics etc). Replacing shaders or re-compiling shaders is not a solution for GCN 1.1/1.2 because AMDs Asynchronous Compute Engines are built to break down complex workloads into smaller, easier to work, workloads. The only way around this issue, if you want to maximize the use of all available compute resources under GCN 1.1/1.2, is to feed the GPU in Parallel... in comes in Mantle, Vulcan and Direct X 12.
People wondering why Fury-X did so poorly in 1080p under DirectX 11 titles? That's your answer.
A video which talks about Ashes of the Singularity in depth: https://www.youtube.com/watch?v=t9UACXikdR0
PS. Don't count on better Direct X 12 drivers from nVIDIA. DirectX 12 is closer to Metal and it's all on the developer to make efficient use of both nVIDIA and AMDs architectures.