Yeah this is something that is largely overlooked. If you look at his game logs you'll that his targets are all over the place. He has only seen 9+ targets once in his career and that was in his rookie season when he went for 13 targets, 10 catches, 157 yards, and a TD.
So when you combine limited opportunity and limited availability, this is what you get. Make no mistake about it, Blockzilla will be back. He will always be back. He's 27 years old so he could be around for several more years. We don't have many examples of WR blocking specialists but it seems like a dude could block well into his 30s.