OK, Ben. Seasoning only on the skin probably is part of it. A little olive oil will lubricate the skin, make the seasoning stick better, and aid in smoke absorption. Duck, if I'm not mistaken, has a lot more natural oils and fat in the skin than chicken, which may explain why the duck gets more brown at the low temp.
Do me a favor - try the recipe I posted above, and see if you get better results. I think the dry skin, and low temp may be part of the problem. Also, get a scale to weigh your wood; it helps. I use a cheap digital scale from Harbor Freight that works great. 2 to 2 1/2 oz of chunks for chicken. You mentioned you "shaved into pencil size;" I would recommend leaving your wood in larger chunks. It looks like the bird in the picture didn't get enough smoke...did it have a good smoke flavor?
Just a thought to help...try to duplicate someone's successful recipe (doesn't have to be mine), and see if your results are the same.