Like it, or not, we have been living with ratings for a while now, and rating systems are even popular and used strategically in the commercial world. Stock, credit, employees, movies, music, performers, and also perfumes are rated on a current basis. But only few rating systems are objective, and it belongs to the nature of such systems that ratings can only statistically be correct. Polls are sometimes subject to manipulation. And good old Chanel (as the best known example) wouldn't be the same today was there not a huge team of highly paid marketing pros in it's back! I think we can all see that. - Now can there be more precise terms than over-/underrated to express anybodies disagreement with public ratings and managed opinions? If ratings are subjective - why must I try to be objective criticizing them? Anyhow, the terms you want to dismiss are used in the real world daily, and I read little criticism about their use elsewhere.
"overrated shares" 1'840'000 entries listed (Google)