Does your MtB have the older/traditional canti brakes? If so then they matched the cable pull specs. to the levers that work with the cantis (and not the current long pull brakes and levers). Also many think that disk brakes should have stronger initial power, being described as more better. But disks have less initial bite, especially if they have not been bedded in properly. They only excel in conditions that rim brakes suffer in. But if your LBS did miss choose the calipers then they do owe you an explanation and the correction. Andy.