You said "The Dual pixel does not hinder AF performance" and then said "Let me repeat it, Dual Pixel does not hinder the ISO"....did my confusion arise because you meant to say ISO performance instead of AF performance in your first post?
And hasn't the Nikon D7100 been tested to be close to 2 stops better at high ISO than the 7d? I didn't do any side by side comparisons but definitely felt like my level of satisfaction with ISO 6400 on the D7100 was similar to that felt with ISO 1600 on the 7D...at least in terms of where I felt I wanted to cap my high ISO usage for the respective bodies....maybe to be fair 1600 on the 7D is more like 4000 on the D7100 than 6400.
There is perceptually better and actually better. There is most definitely a psychological component to thinking that the D7100 is "two stops" better at high ISO. From a technical standpoint, it probably isn't possible to actually get truly two stops better, since stops are a power of two, and ISO performance is dependent upon Q.E. and pixel area. The 7D has larger pixels (4.16µm vs. 3.91µm), which is it's benefit, where as the D7100 has more Q.E. (but certainly not enough to literally be two stops better.) The D7100 has 11% better Q.E. than the 7D (52% vs. 41%). In terms of pixel area, the 7D pixels are 13% larger. Technologically, the D7100 has a better sensor with a better architecture, which also probably gives it an edge when it comes to high ISO (primarily, it has a higher SNR, which means that at every ISO, it has a larger usable signal). Overall, from a literal, physical, technical standpoint, the difference between these two sensors is fairly small, and while the D7100, thanks to its excellent SNR, does better, it isn't anywhere close to two stops (i.e. the 7D at ISO 6400 has a saturation point of 536 vs. the D7100 at ISO 6400 which has a saturation point of 541...almost negligible.)
To truly have a full two stops better noise performance, where the amount of noise at ISO 6400 is the same as the amount of noise at ISO 1600, you either need to reduce megapixel count by a factor of two (pixels that are four times greater area...i.e. a pixel pitch of 7.82µm)...or you need to increase quantum efficiency by two orders of magnitude. The 7D has a Q.E. of 41%. Twice the efficiency is 82%. Twice that is 164%. Well, it's impossible to gather more photons than exist, so you can't have more than 100% Q.E. (and achieving that usually requires rather bulky cooling equipment that would render such a camera immobile.)
From a perceptual standpoint...softer detail appears to suffer more from noise. The 7D has an AA filter, where as the D7100 does not. The D7100 is going to have much sharper detail due to having more acutance. THIS is its true strong point when it comes to ISO performance, and probably the key reason why it "feels" as though it has less noise. Detail is sharper with the D7100, so noise doesn't appear to be as prevalent, even though it is roughly the same as the 7D. There is a tradeoff for this...more aliasing and moire. General aliasing can be delt with to a degree with downsampling, moire can be very difficult to deal with (there are some tools, however most simply reduce color moire and mitigate monochrome moire, but none can actually eliminate it.)
If you don't shoot subjects that have repeating patterns or clean edges that might result in aliasing, then the D7100 is certainly an amazing camera, and its sharper detail will certainly result in perceptually less noise.
The 70D is still using the same general sensor design and architecture as the 7D, so it is doubtful much of its weaknesses have been resolved. I get the feeling that the 70D is sharper, which will go a long way to mitigating how noisy it "feels". It has a larger signal, however again thanks to Canon's read-noisy archaic sensor+ADC architecture, it still isn't as good as the D7100 (26726e- vs. 29236e- FWC.) The 70D also still uses an AA filter, which is going to soften detail around nyquist...and while that eliminates (or greatly reduces) aliasing, the lower acutance will still make it "feel" as though it is noisier...dual pixel architecture or not.
Really informative post, very interesting about the affect of an AA filter on noise perception. I wonder if Canon will begin going the Nikon route and moving AA filters.