It isn't just the sugar in the rub. Too much rub - think shake and bake layer- can also do this. On pork butts and everything. Medium layer so you can still see the meat is the way i've learned to do it now.
I did a bird last year with just kosher salt and course pepper like Franklin does in hisbPBS his pbe video and loved it. I'll hopefully be doing another next weekend. I don't like BBQ rubs on poultry. I like traditional. Give it a shot.
Proudly Smoking on a UDS, PBC &
Accidental Winner of the 2012 "Saucy" Throwdown.