Dean on top would not cause a ratings boost. Because Vince wouldn't allow it. Vince has his mind set on one guy, and you all know who I am talking about. And only that guy is going to be allowed any focus going forward. Vince thinks he can force this guy's overness and create something, unlike letting something grow organically. There are, as of this writing according to what few sources I have, no wrestlemania plan for Dean (and there hasn't been one since they started putting together the card) of note. And there wasn't even one for Seth either. They had a guy get an 8 month run with the belt, put on some of the best matches in a while and really grow and get over, but Vince refused to plan him into anything meaningful at mania 32 in favor of his guy.
TLDR: Vince doesn't care who we want on top or like or are willing to watch. He only cares about who he wants on top and is trying to force a ratings increase through him.
And that's not going to work, it never has and never will.