I would disagree with you. How do you know that Sauron, Saruman, and Morgoth were poor at personal combat? Sauron killed two lords with enchanted weapon when he was trapped by the Last Alliance.Saruman may have been poor in combat, but we don't know; he made journeys into the dark, shadowy and evil East, so it might be reasoned that he could have gotten himself into tough spots where he had to fight.

The Witch-King and the Narzgul together were fearsome enough to make even Aragon and Glorfindel be afraid of entering direct combat with them; yet they were also competent commanders.Glamrung is named Dragon-lord of Orks once, so he is apparently a commander of some sort.