My F250 6.2 likes to drop gears and wind up pretty easily. Torque curve on these engines appears to be abysmal below 3000rpms. That said pulling a decent load I feel the trans does a good job of picking the right gear for the conditions possibly with the exception of hanging up a little too long in a lower gear after cresting a hill. But that is only the case if the road is straight and fast and you're lookin to gain some steam going downhill. On slower or winding roads it seems appropriate.
I'd get it checked out if its dropping too low or hanging too long in that gear. If its only replicated by towing then set it up w the dealer to bring your truck in for a loaded up test drive over a cpl hills.