I think one of the big reasons (my assumption) for the issue of QBs is that teams will spend huge draft capital to move up to get a QB as opposed to moving down and collecting more picks.
Also, the pick of a QB is so consequential in that the amount of personal attention and coaching they must receive, and that offenses and to some extent systems are built around QBs. So, when a QB fails, it can involve new coaches, new systems, starting the learning process all over again, new and different players to surround the QB that fit his skills, etc.
As for a WR, I think that is just an extraordinary failure rate. And, for every QB, dozens of WRs become available. There is no need to take a chance on a WR when you stand just as good a chance at getting a good one later.
So, I suspect that from this we are to take it that these are the 2 worst positions to take early. And, I'd have to say that anecdotally that's what I see. You have a better chance of almost any other position panning out as a 1st round pick than a QB, and 2nd as a WR.
