I was worried about the same thing, but I was surprised to find that there is actually more variation in lighter tones than I originally thought there would be. I do feel that the problem lies in combining these new skin tones with the limited to no variation of natural hair colours.
The highly saturated hair-hues make some of the skin tones appear duller, whereas if there were additional hair colours with hue & brightness options similar to the skin tone sliders, I believe it will improve the balance overall and both elements would look so much better together.
Right now I think there is just an imbalance between natural skin tones and natural hair colour.
