I think we (Disney message board fanatics) tend to underestimate certain things, such as sometimes needing to be a little blatant to get things across to the average park guest. I can't tell you how many times, during WoC construction, I heard people say that it was a new ride, a submarine ride, etc, when they looked at the structures being built. The funny part: this would always be RIGHT in front of the signs/artwork that explained exactly what WoC was going to be. My point here is that sometimes Disney needs to be a little bit "on the nose" when it comes to things like this.
As for Disneyland not needing a huge Mickey head... well... first of all, they do have one, right inside the ticket turnstiles. They also have the advantage of having been there for 55 years and being the first park at the DLR, so people are a lot more familiar with it. It doesn't have a land with a reputation that needs to be fixed.
Ultimately, Disneyland "rules" don't necessarily apply in the same manner at DCA. DCA needs to prove to people that it's not what people thought it was, while Disneyland doesn't need to prove anything. Everyone grew up visiting it, and knowing what it's "all about." DCA has a very tough task as they try to prove that it has the same broad appeal that DL does and therefore they have to, on occasion, be a little bit too obvious about the fact that things have changed. Simply removing the scary metal sun from the wheel would help, but I honestly think it was somewhat necessary for them to put something there that screams at you "this attraction is different now." While the ride itself isn't literally different, people subconsciously sense it when there's a big, classic style Mickey face on it. A blank space there wouldn't accomplish the same thing, especially for the "common guest." I don't mean that in a derogatory sense, it's just that a theme park can be overwhelming when you don't study it in-depth, and sometimes simple, straightforward icons like a giant Mickey face can make things a lot easier for someone who isn't a hardcore fan.