Now regarding the Ranger defense, the Rangers have two RHD that can play top 4 mins, so it isn't a pressing need as much as having a PP QB that can do his job, and that's something DZ hasn't done since his rookie year. Can DZ get his swag back?
Off the top of my head the following players are RHD that can QB the PP, and play top 4 minutes:
Doughty, Karlsson, Weber, Subban, Boyle, Shattenkirk, Zidlicky, Faulk, Letang, Byfuglien, Green, Schultz, and Voynov. And are the guys I would move DZ for except for Buff (300 lbs), Zid (UFA). Now how many are available, and what is the cost both in terms or assets, and the cap?
That is how you get an upgrade on DZ without replacing the newest whipping boy internally.
I agree that DZ isn't the same player on his off side, but Torts never played McD or Moore on that side so we don't know what they can do. Staal and Girardi made a pretty good shut down pair too, so it's not as if moving McD to the right is going to create a huge hole.