Lower the price to $499 permanently, increase base storage to 64GB. I'm not even sure that would help but it's a start. OP3 and Axon 7 are really sticking it to high end android phones. Unfortunately, HTC is caught between a rock and a hard place. They can't survive on brand recognition, they don't have a loyal following like Apple and have has some bad misfires (M8 and M9). The 10 is the best phone they've made ever, but the competition has caught up and in some ways surpassed them. The answer is keep trying to compete on high end specs,(which isn't working) or compete on price and offer more.
OP3, ZTE, Alcatel and other mid rangers are offering more bang for the buck.