It's possible Zad has leveled up, and can play top four minutes. I think that's what he wanted and we'll get to see how it plays out this season. It's possible Vancouver didn't see him succeeding in that role
Everyone knows how strong he is, and if his play is more consistent, then the value will be there for the contract. A really fun guy to have on your team and he'll definitely be missed.
Downside is if he plays like a bottom pairing guy with costly turn overs and missed assignments. Canucks fans got to see that from Myers for most of his tenure with the Canucks, so that kind of play can really effect a team. If he's only a bottom pairing guy, 5 million seems like a big hit.
Personally, I think he's worth the gamble.