It's not really about agreeing or disagreeing with regards to power vs noise floor... That's just what it is.
As far as how much power is enough for optimal sound, I agree that a bit more power than will ever be needed is the best solution for any speaker... Full size, headphone, IEM, whatever... I believe all benefit from a small allowance over maximum requirement. What I am saying is that with many of these newer tiny mobile devices, there is a point where the power far exceeds what is realistically needed, and this impacts the refinement and noise floor of the device.
Let's say you had some full size B&W Nautilus speakers. Lucky you. But if you hooked them up to whatever amp NASA uses for the shuttle launch speakers, you'd get a polluted noise floor. You don't need to drive truck-sized speakers designed to count down a rocket launch with your home theatre amp, so at that point, the excess power is detrimental to your setup and the overall sound.
When I look at something the size of the Mojo, I don't see a whole lot of people plugging a set of LCD3s into it. Some will, sure. Probably to see if it can drive them, and they'll be impressed when it does. But realistically, that's a parlor trick. There are a plethora of other solutions available for difficult full-size cans.
Basically, I'm pointing out that most cans that are difficult to drive aren't usually used as mobile solutions, and the Mojo is clearly a mobile device. The power required to drive big difficult cans far, far exceeds even the most difficult IEMs by a wide margin. That's why you if you put that power into a sensitive IEM you get a polluted noise floor. But if you throw out the unnecessary ability to drive very difficult full-size cans, draw that power back to just a bit more power than the most difficult IEM will draw, you get improved refinement, a blacker noise floor, and still more power than you'll ever need, meaning whatever improvements the sound from your IEMs may require, it won't be for a lack of power.
In my estimation, this makes more sense for how something like the Mojo will most likely be really used.