For default, I actually don't mind the MU, to the dismay of many Rosalina mains in my area.
While doggy is a great "zoner" and camper, he really does get a ton off of one projectile. Doggy never has to approach in this MU if he gets the percent lead, and Rosalina can't absorb the gunmens' projectiles, two fantastic points against one of the highest rated characters in the game (#1 in my opinion, or tied with Sheik at least). If Rosalina has the percent lead though, she still has to approach, which is annoying.
Clay Pigeon follows up into fair, as well as "locks" Luma in place if she is by herself, not being able to do much. Trick Shot may be the worst projectile to use offensively, but I like to set it up in the middle of the stage to bait the gravitational pull. Once the opponent catches onto the baiting, then it gets it's functionality as a trap if she ignores it. As I mentioned, gunmen can't be absorbed, and hits Luma even when shielding, getting rid of Luma if Rosa is on the ledge.
Rosalina still has better KO and combo potential, not to mention safe pressure if she is able to get Luma out.
I'd say it' s +1 in Rosa's favor. While she has great tools, the fact that Doggy never has to approach means you can't just sweep through the MU.