His lack of production is more than likely due to his centering what is essentially the 3rd line. A couple weeks into the season, Butler separated Terrance and Spence. Spence moved to a line with Fimis and Alfano, and that line has been, by and large, the best forward line.
Terrance now has Edwards and Royston as his wingers. Edwards put up great numbers last season, but as this season goes on, it's looking more and more like he was a product of playing with Fimis/Alfano. Royston is a big body, but lacks the skills and finesse to be playing routinely on a skilled line.
Terrance has played great. Better at faceoffs this season, is in the right spot and the right times, back checks really well. He's just struggling to produce because his linemates are struggling to produce. Anytime you see him on a penalty kill with Spence, a 4 on 4 situation, or on the power play, he's playing fantastic.