My Dometic 15K AC does a great job, cooling my 31" FW. I also think it has more to do with the insulation and build quality, rather than an AC not doing the job. My FW is described as 4 season, and is the most quiet inside of the 4 I have owned. Does your coach seem stick house quiet, when camped in a RV park, or does it sound like the door and a window or two are open? That describes my previous FW! :)
I can start mine any time, even when temps are high inside, and it catches up, slows to low fan as temp gets near stat set temp. It then cycles on/off when set on auto, but never needs to return to high fan to keep up.
Jerry