The most important thing to know is what the trade protection is. The Rangers currently sit with the 12th OA pick. If it's top 5 protection or better, I'd call that a huge win for the Canucks because there is a reasonable chance the Rangers finish in the 8th to 14th type wheelhouse.
Of course, there is a chance that they turn it around and make the playoffs, but otherwise if they can end up with a top 10 type prospect in return for a disgruntled star player with a NMC, that's very good.
If it is playoff protected, it's very bad - but you at least have the slim chance that Miller could be such a jerk that the Rangers lose again next year and you get a free and clear shit at McKenna in the lottery...