Yeah, he didn't live up to nearly anyone's expectations last year.

He had more yards than Gonzo, Gates, Witten, and Graham did in their rookie seasons. If anyone was expecting startable numbers from him as a rookie in a committee, their expectations were ridiculous in the first place. His rookie year was fine. Once Gresham is shown the door after next season he should be a perennial top 10 guy at his position. He could even do it next year depending on how much he improves and how heavily they feature him.
I think he's a fine investment for the future. The hype last year was ridiculous though. Right or not, expectations were set remarkably high... Hence my buy if you like him earlier. It's hard to gage the tangible numbers people expected but I'd say it was in the range of 650 yds, 4 TDs. He delivered 445 yds and 2 TDs.
Worse yet, 3 other rookie TEs severely out produced him. Had you said he would rank as TE30 overall and TE4 among rookies in August of last year FBG may have banned you. But, that exactly what happened.
Reed and whom else?
Ertz and Wright.
Here are the numbers for last year's prominent rookie TEs:
Jordan Reed - 59 targets, 499 yards, 3 TDs (8.45 yards per target)
Zach Ertz - 56 targets, 469 yards, 4 TDs (8.38 yards per target)
Tim Wright - 76 targets, 571 yards, 5 TDs (7.51 yards per target)
Tyler Eifert - 59 targets, 445 yards, 2 TDs (7.55 yards per target)
Mychal Rivera - 60 targets, 407 yards, 4 TDs (6.78 yards per target)
I'd be somewhat reluctant to say that anyone on this list "severely outproduced" the others. Wright had the most yards, but that's easily explained by him also having the most targets. Reed and Ertz were a little more effective than Wright and Eifert with their targets. However, the difference is so small that one single big catch could swing the pendulum either way. So to me, their numbers are close enough that they basically fall within the same general range and any separation could be attributed to random variance more than significant differences in performance.
It's a moot point really because arguing that Ertz, Wright, and Reed had strong rookie seasons doesn't ultimately address the question of whether or not Eifert had a strong rookie season. If I said Demaryius Thomas had a great 2013 season and your rebuttal was to pull up stats for Dez Bryant, Vincent Jackson, and Brandon Marshall, have you actually addressed my question in any way? Not really. If ALL of those other receivers had great seasons, it doesn't somehow mean that Demaryius didn't also have a great season.
The idea that Eifert had a disappointing rookie year is pretty weak when his numbers were not only on par with (or even better than) most of the best TEs in his draft class, but also most of the best TEs in recent NFL history at the same stage of their development. He didn't quite light it up like Rob Gronkowski or Aaron Hernandez. Short of that, he was fine. Statistically, I don't see much in his numbers that justifies a downgrade. It's just bad analysis to panic over a quiet season by a rookie TE. Especially when he's sharing the field with another first round TE who just had a top 10 season the year before. Bad situation + being a rookie at a position where rookies don't usually make an impact = nobody should've expected a big impact in his rookie year.