Zadina was not a center and depending upon team system, centers are a little more valued, JV did move to wing a bit (as he was moved around) and honestly, I don't fully understand the wings criteria for their advanced stats yet, but they must see some value of JV above other options (they did have Fisher pull center duties a bit last year) available out there.
JV filled a swiss army knife role last year and from memory, much of his -16 (like many like Raymond) came during the horrid streak when both Larkin and Compher were out and they were into massive shifting of what centers they did have into slots they should not be in for any great length of time.
I am OK with the JV price tag, it is market value, I agree the term is a little of a head scratcher, but SY did give JV a prove it deal last year, he proved he is a serviceable bottom 6 willing to do as asked.
I suspect the 2 years is so SY will not have to revisit things in a year, but it also makes him much easier to trade as he has a relatively low cap hit with term and he is a natural center. (I still think SY will make some hockey trades before US Thanksgiving, at least one for a serviceable #2 pair RD, which will have a cost to it, I see JV, Lyons or Ras likely as part of that along with shipping out Holl, but that is another thread discussion)
Looking at the PK/PP (using the 4/8f forward assignment) alignments today, JV is one of the swiss army knifes that can platoon between the two. Even if he is not prefect for either, the versatility versus a Zadina or Sprong does indeed have some value to the team depth.
In the big scheme of things, JV at this cost and term is pretty much a nothing burgher.