I was looking at this map again (and it's well worth at least a second look) and I was wondering if you had the shading on a separate layer from the rest of the artwork. If so, reducing the opacity might mute it just enough to bring it back in harmony with the rest. You might also be able to do a selective muting (draw a mask just along the spines of the main spines of the mountains, blur it somewhat, and then use blurred image as a layer mask) to reduce the shading a bit.

The detail level on those mountains really does look good when contrasted against the more empty areas. It's only when the whole central area grabbed more than about of a quarter of my field of vision that I found it became too much.