I don't see anything wrong with it if you actually know what all that (being a supposed "rockstar" in a field) entails. It only annoys me when I hear it thrown around in general conversation by folks who have no clue what a "insert-programming-language-or-framework-or-markup-language here" rockstar really is and they're just tossing it around because they've heard somebody else say it.
> "Is this a by-product of a job market so oversaturated with incompetence that the employers must resort to extremes to make sure only people with real talent apply"
I think it might be. I figure folks would still just ask for an "expert" in a job description if that concept hadn't been taken up by a bunch of folks that aren't (in fields everywhere--not just writing code).