This is exactly what I thought about the score. Your problems are identical to mine. The "RCP" percussion adds absolutely nothing (and as you said sounds like How to Train your Dragon) to what's going on and in fact covers up his work. I also thought the call backs were too heavy handed during the Kessel Run. I would have preferred an original piece specific to the Kessel Run similar to how Williams writes different pieces for action scenes.
The percussion just annoys me and I'm a percussionist myself. As a good friend of mine said way back in the 7th grade, "Percussion is like salt, too much and you ruin the plate. Too little and the food needs a little spice. When you get it just right it's perfect", or something along those lines.
All that being said, I thought the soundtrack was fantastic without the RCP percussion as it sounds distinctly Star Wars and retains the tone and style of fast moving brass and strings perfectly.