Since defensemen play more minutes than forwards, let's just look at forwards for ice-time for a moment.
Among Coyotes forwards, Galchenyuk was 9th in even strength scoring. He was also 9th in even strength time on ice.
As it turns out, despite there being 9 defensemen who averaged more even strength time on ice per game than Galchenyuk, only one (Ekman-Larsson) was above Galchenyuk in even strength points.
Galchenyuk was 3rd on the Coyotes for Power Play Time on Ice, though, at 3:10 per game, which helped contribute to him being tied for 2nd in points per game on the team.
Of course, Galchenyuk's 0.57 points/game would only place 5th on the Pens this past season (Crosby 1.27, Malkin 1.06, Kessel 1.00, Guentzel 0.93; Hornqvist was next at 0.54).
All of this goes to show that it's pretty easy to cherry pick stats to support whatever narrative you want. Yes, Galchenyuk is a downgrade from Kessel on offense. But he's not bad at even strength. Half his points came at even strength, after all.
Galchenyuk has never played with a center remotely close to the caliber of Crosby or Malkin, and since he's still in his prime, it's not unreasonable to think that his production should increase a little with the superior line-mates he'll have here. He won't match Kessel, but he should be better than he was in MTL or ARI.