Yeah, I'm unconvinced about Demers being an upgrade as well.
And either way, my main issue with acquiring him is that I think you should avoid clogging up your cap with mid-level talent making mid-to-high level money at all costs. We've already got Zaitsev on his deal for six more years, and if you acquire Demers too, all of a sudden you've got two OK secondary RHD options on defense taking up almost a combined $10M of our cap for the next three-and-a-half seasons.
If we acquire help on defense, I think we have to do it one of two ways:
1) If it's someone with term, they have to be a definite top-pairing guy, and at least a clear upgrade on every Leaf D-man not named Morgan Rielly.
2) If it's secondary-level talent like Demers, they need to have very little term remaining; either on an expiring contract, or a contract that expires after next season.
So keeping that in mind, if we're talking about the Coyotes, the guy I'd be interested in from them would be Hjalmarsson.