Rangers decline and it's honestly not rly close. Not sure why you're underrating Deangelo like this...
He's basically Roman Josi at this point.
Here's an easy way of thinking about this:
Josi seems clearly better right?
Now consider that Deangelo spent 50% of his ice time with Marc Staal while Josi spent 57% of his ice time with Ryan Ellis, about the same...how does that grade out?
Heck, seeing that you might think that Deangelo is a younger, cheaper (thus more valuable) version of Josi and you'd be correct.
It's weird how little you're capitalizing on such a great asset...