All the fossil evidence we have indicates that dinosaurs were the precursor species to modern birds, which are most certainly homeothermic. So, we can presume that this mesothermy is such that the dinos need not bask in the sun to maintain body temperature.
Mesothermy has nothing to do with endurance. In fact, the relationship may actually be inverted: the dinos with their lower basal metabolisms for a given body mass than placental mammals (much as marsupial mammals have) would use less energy for the basic processes of life, and activity would generate body heat and raised body temperatures which they would be better able to tolerate despite potentially worse thermoregulatory capability than humans.
As a side note, there is practically no creature on earth that is as good at getting rid of excess body heat as humans... but getting rid of excess heat is not the only way to cope with body heat, the other way is to simply tolerate it, and continue to function despite an increased body temperature. The nature of thermodynamics is that the higher the difference in temperature between two environments, the faster heat will be radiated away from the hotter object. So, the dinos body temperatures may vary by several degrees during exertion, but unlike mammals, they can simply put up with it.
A dromaeosaur descendant would have a largely horizontal spine, much like birds which also are thought to have descended from dromaeosaurs, though the possibility certainly exists for them to rotate their hips so that they are standing more upright.
The dromaeosaur body plan includes legs with muscular thighs, slender calves, and a digitigrade posture with extended foot bones, making them a cursorial species. Humans are the fastest of the apes in bipedal locomotion (though apes which move quadrupedally may be faster), and can run at up to 37 kph or so. However, humans' relatively short foot and bulky calf muscles do not allow as efficient or as rapid running as the dromaeosaur body plan. While ostriches can run at up to 80 kph, I would expect that a dromaeosaur such as the OP's dinos would be able to run at around 60 kph or so, and could conceivably leap two or more metres upwards and perhaps up to ten metres laterally.
While humans are effectively unarmoured and have no claws or fangs, medieval humans such as the OP mentions are able to supplement their meagre natural weapons and armor with manufactured weapons and armor. On the other hand, the dinos, being carnivorous predatory beings, would have tough skin overlaid by feathers, as well as long claws on the fingers and a particularly large claw on each foot. Additionally, the OP has said that dinos have a humanlike ability to make their own technological innovations. This could include their own armour and enhanced weapons such as razor sharp claw sheaths.
Given a dino's long, narrow body plan and well-made metal armour, I would expect that arrows and other thrusting weapons would be more likely to deflect from their armour than is the case with a tall, broad human figure. This, combined with dinos' great mobility, would render the mainstay of late medieval military armament - pike and shot - far less effective than it is against humans. Dinos could reasonably expect arrows or spears to deflect from their armour, and combined with their mobility, they could either throw all but the most disciplined phalanx into disarray simply by flanking, and if the phalanx sacrificed its own mobility and formed a circle, the dinos could still duck under or leap over the spears and once inside the range of the spears, their enhanced natural weapons would quickly break the phalanx.
A unit of sword wielding humans would stand a better chance against the dinos than pike and shot, as swords are inherently more maneuverable weapons.
Human cavalry would have speed approaching that of the dinos, but lower maneuverability.
The main advantage that the dinos have is that they have intelligence comparable to that of humans. Combined with their superior natural weapons, they could maneuver humans into situations where the dinos advantages could be exploited to the fullest.