What I see as the most extraordinary claim here is that we should extrapolate what happened to Asuka to the rest of the world.
That's not extraordinary in the least. Yui specifically says that all beings have the power to return to human form. There's nothing ambiguous about this statement: all beings have the power, period. All the have to do is be able to "imagine themselves in their own heart," whatever the hell that means. There is absolutely no reason whatsoever to think Asuka alone has this ability, particularly since Yui just said every living thing has it.
NemZ pointed out 2 different things. Firstly, that the process Rei describes sounds paradoxical and that she herself only said that it can happen, not that it will.
No. She said that when AT Fields returned people would
feel pain. There was no qualifier there -- if she ended Instrumentality, people would feel pain again. You can't feel pain if you're a soup of LCL, so that means people would have to re-embody before they could hurt one another again. And lo, Asuka comes back and she and Shinji hurt one another, just as Rei said they would. There is nothing remotely paradoxical about this.
The next question is how many people will actually do that. You take it as a given that the number- will at least be bigger than 1. Of course I accept it might be, but why is it a given?
Because Yui said so.
Look, here's the basic problem with your argument: it isn't a natural reading of what's presented on the screen. Rei and Kaworu tell us what will happen, Yui gives her inspirational little speech, the Black Moon is destroyed and the souls of the world released, Asuka comes back, Shinji and Asuka hurt one another exactly as Rei said they would. The natural reading is that this is indicative of what's going on around the world (since we saw all the souls released and Yui specifically said every living thing had the power to come back). You're the one who's claiming that Asuka's the only one who's chosen to exercise this power, and you'll need a pretty compelling argument to get anyone to take said claim seriously. So far you haven't provided one.
Either way, things have become pretty hellish. The only question is how hellish.
We don't actually know that, and it's beside the point anyway.