I don't know that too much rub would dry the meat...did you let the ribs sit overnight in the fridge after the rub? This might help. Most of us now use the "no peaky" method for ribs...let them go 4 to 4.5 hours, and then if you want, you can remove and sauce before the last hour or so of the smoke. I take my ribs out at 4.5 hours, sauce them, and then back into the smoker for the last hour. This is an optional step, but one that my family likes.