I actually somewhat agree with the original poster, and I had him ranked as the #1 TE.
The thing is, he probably should have been higher on overall draft boards (at least in PPR leagues), not only based on the great numbers he's putting up, but also largely based on the mediocre to poor #s the rest of the TEs are putting up.
IMO, there aren't even 10 startable TEs when they're all healthy, and a number of the startable ones like Dallas Clark, Shockey, and now Sheffler are missing games due to injury. The only two I thought were worth mentioning with Witten coming into the season (Gates and Winslow) have both under-performed with one battling a lingering injury and the other on a questionable offense. And of course there are the black-hole busts like Vernon and Heap (though he's at least shown something). Others like Cooley, T-gonz, and Owen Daniels are all respectable enough but are getting outscored by a huge margin by Witten, and I'd expect that to stay the same going forward barring injuries.
Without crunching numbers, Witten might have merited being drafted as high as 20 in a PPR redraft, and I'd think surely at least by pick 30. To be honest, if I received a trade offer of say Wayne for Witten straight up, I might not pull the trigger as the drop-off with a replacement TE might end up being starker than a replacement WR. In these respects, he was indeed under-estimated.
All of my analysis is based on PPR