take a look at the league leaders in drops every year. last year some notables were, desean jackson, miles austin, wes welker, steve smith (x2), mike williams, and sanatonio holmes. there are some elite recievers on that list. does that make them overrated? When judging if a player is overrated or not you cant look at 1 year of stats. yes brandon had a dissapointing year stat wise last year. but overall talent wise hes still one of the best in the league and one of the most dangerous. just a year ago he set the record for most catches in a game. not to mention hes also one of the best blocking wideouts in the game today.
As for Vontae i guess it depends how you value him. if you see if as an elite WR then yes, he probably is overrated, I don't think hes quite there yet. But i don't see him as that so to me hes not overrated. overrating and underrating a player is all based on how YOU view them and then its opinion after that.
As someone else said dropped passes is subjective, but even within that assumption, I think it's easy to agree that dropping passes decreases the value of a receiver. If you're leading the league in drops it's X number of plays you didn't make.
I agree with the general point that their valuations are subjective, that with a good performance this year the perception can change, and most of all, that perceptions of value are fleeting and vague.