No the essence of sybil is that you can make one appear to be many (and get more votes or whatever benefit it is from appearing to be many). You can't do that with ASICs. One is just one.
Everyone is using ASICs now so there isn't really anything disproportionate about it.
An ASIC is one. One chip, custom designed to only do hashes. That's disproportionate power in its essence.
That's silly. It's like saying that everyone has to do hashes with pencil and paper.
The reason ASICs are a problem is that very few people have the ability to develop and manufacture them so it is a cocentration of power. There is not really a sybil attack, since no one is claiming otherwise. We are perfectly well aware there are only a few ASIC developers and there will probably be fewer in a year or two.