But for only for AMD products ... could the power issue be an "architectural defect" at 14nm with regard to attaining a certain level of performance?
I don't see what you mean really. The power draw from the motherboard and the molex is PCB design, unrelated to the manufacturing process of the GPU.
The amount of power necessary to achieve a particular benchmark score depends on lithographic process, architecture
and design targets. The last is important. If AMD had produced a P10 with, say, 44CUs (+TMUs, ROPs) running at 1.05V and using GDDR5X at a leisurely 10Gbps, they could have hit the same performance at a much lower power draw,
but higher cost. The existing RX 480 can reduce power draw significantly while loosing relatively little performance, giving the impression that for whatever reason, the product was pushed a bit outside where it is happiest. Which incidentally suggests that it will do well when you back off a bit in mobile or more thermally constrained environments such as iMacs.
It's a game of skill and compromise. We cannot know how competitive Global Foundries 14nm process is compared to TSMC for these types of products. Nor about design tool glitches, process variance, defect rate...the list goes on and on. I think it is a given that both nVidia and AMD do the best they possibly can to come up with viable products. Overall, IMHO, they are relatively close in what they deliver regarded as a whole. Differences in where they compromise, and where they decide to introduce new capabilities is the air this forum breathes for its discussions.