I'm not sure what the advanced statistics say, but his standard statistics show that he's largely been the same player each of his 3 seasons. 20 minute, 2nd pairing, defensive defenseman. His rookie year scoring was an outlier. Over the past two years he's on a scoring pace of 7 points per 82 games. Really the only statistical change this year is that his hits and takeaways have increased. That's not a surprise, since the eye-test says that he's been more physical this year.
In terms of his contract, there aren't many comparables to him. I imagine his agent will try to get him something like the Brett Pesce contract. The Connor Murphy contract might be another one, but that's from almost 3 years ago. However, both were scoring at double his pace.