I agree that there really isn't a WDW parallel for DCA but many would say DHS because it has the lowest of the four parks attendance and it's just not as good as it used to be. I think DHS could really benefit from a DCA style make over but I don't necessarily think it needs it. What it does need tho is something large and new like Star Wars land or something.
DHS is missing a couple of things. First and foremost, they need an e-ticket style on the east side of the park. Hopefully this will be addressed with a Star Wars expansion, and it will be a bit of a thrill ride. A lot of the traffic is concentrated on Sunset and in Pixar Place, have to get the crowds over to the other side more.
Secondly, they need more attractions for the entire family. Tower of Terror, Rock n Roller Coaster, and Star Tours are all height restricted to at least 40" or more. They would do well to add some sort of spinner type to a Star Wars expansion.
Third, they need to figure out what they want the backlot (south side of the park) to be. I think they could do better than the Backlot Tour and LMA, but that is a pretty big area that would cost a ton of money to reconfigure and retheme.
Finally, another dark ride would do well there I think, maybe something with Pixar back in Pixar Place or the Muppets near MuppetVision.
The biggest thing would be the Star Wars expansion. Get that in, and then you can address the backlot afterwards (or kill two birds with one stone if you use that area as the expansion plot).