Dzingle did put up just outside 1st line number last year and so far this year 1st line numbers. Lower end so he obviously will not be traded to a team needing a top line LW, but he is easily a 2nd line winger on just about every team in this league.
Whats the going rate for a player who is 33rd in scoring at his position over last year and this? That also included 22nd in goals last year, 14th this year? I'd think its at least Tatar territory.
Dizingel has a single 20 goal season under his belt, and while he seems like a solid player, I don't think contending teams will be looking for him to take on a prominent scoring role, it will be to bolster their depth. Maybe he is a fit on a 2nd line if a contender really likes their 3rd line as is, but in general, I think he's viewed as a good top 9 forward.
I don't think the Tatar trade is a reasonable expectation for the value for Dzingel. Tatar was in the midst of his 6th straight season scoring at a 20+ goal pace, and he had term left on his deal, so he wasn't a rental, so his value would have been more than Dzingel's. Also, that trade was a highly visible failure for Vegas that looked like an overpay at the time, and looks even worse since, so that trade won't be setting a market for UFA forwards.