The problem was that you cooked the chicken too long. Poultry needs to be cooked to an internal temperature of 165 degrees F. At 170-plus, the chicken is already overcooked. Factor in the holding time and carryover cooking, that chicken was simply exposed to heat for too long. Next time, take the chicken out when the internal temp. reaches 165 F. Also, besides the marinade, make a teriyaki glaze or sauce that you can pour over the chicken once it's cut up and ready to serve. This will also add moisture to the meat and hide some of the dryness.
"Boldness has genius, power, and magic in it."
Johann Wolfgang Von Goethe