Trouba's best year as a Jet was 18/19 when he was paired on the first D pair with Josh Morrissey. That was also Josh Morrissey's best year. They just worked really well together, and each looked worse after the trade.
Trouba also benefitted greatly from Byfuglien's injuries that same year, as he got prime PP time on what was then one of the better power plays in the NHL. He didn't really belong in that spot to be honest, but with Byfuglien gone, he was put in that position and collected a bunch of points.
Bottom line to me: Trouba really benefitted from being on a solid D core from top to bottom in Winnipeg for a couple of years (Trouba, Myers, Byfuglien, Morrissey, Chiarot, Kulikov was a solid D), worked well specifically with Morrissey, and hit the PP jackpot with Buff's injury. He turned that into a contract that pays him $2 million more per year than it should.
He's still a good player, I just don't think he can carry a top line D pair all by himself.
From my perspective as a Jets fan, I think Jacob Trouba is better than Neal Pionk. I think Neal Pionk and that first round pick (Ville Heinola looks legit) is better than Jacob Trouba though, especially when you factor in that Pionk is earning $5 million per year less than Trouba.