I have no place for dragonborn; they do not fit in the slightest with my conception of dragons. I don't see dragons as wanting or needing a servitor race. Moreover, the dragonborn "honorable warrior" ethos is wildly at odds with the typical dragon personality in my world (laconic, arrogant, playful in a predatory way).
What I intend to do instead is strip off the fluff and re-do them as follows. Note that "demonspawn" are slightly re-flavored tieflings.
Furies are a race of hell-spawned warriors, the offspring of humans and devils.
Furies are terrifying creatures who live for war. They are very tall, females being six to six and a half feet and males sometimes reaching a height of seven feet or more. Their bodies are lean and hard-muscled, and their black hair is usually worn long and loose. Their faces are fearsome to look upon, with sharp fangs, heavy ridges sweeping back from their brows and cheekbones, deathly white skin, and crimson eyes that burn with the flame of Hell when they go into battle. Some of the more powerful furies grow black-feathered wings, and can hurl blasts of fire, bolts of lightning, gusts of freezing wind, or gouts of vitriol from their clawed hands.
The furies were bred by the lords of the Nine Hells to lead the infernal legions in the War of Fire. Curiously, just as demonspawn are subtle and charming despite the savagery of their Abyssal sires, furies lack the calculating nature of the devils that made them. Instead, they are filled with an overwhelming lust for slaughter. They relish martial contests, and disdain the underhanded tactics often favored by their kin. To a fury, victory is only sweet if it is gained in open battle against a mighty foe. Some furies are sullen and humorless, while others are full of laughter and daring, but all of them find the purest joy of their existence in the clash of swords.
Since the end of the War of Fire and the banishment of their masters, the furies have wandered the world. They are not fond of one another, and an encounter between two furies typically ends in a duel. They breed true with humans, however; the child of a human and a fury is always another fury, and this has enabled them to replenish their numbers. Since a fury born to a human woman is usually killed at birth, most are the offspring of female furies and human men. Fury mothers train their children from birth in the ways of war, and will fight savagely to protect them. The bond between mother and child is the only connection most furies have with others of their kind.
Not all furies follow the evil ways of their creators. Many become mercenaries, and a few--usually those who were raised by human mothers despite their infernal heritage--even devote themselves to the cause of good, turning their bloodlust against the evil creatures of the world. This is all fairly academic to most humans, however, who will gladly kill any fury they can. Furies quickly learn to conceal their true nature, wearing gloves over their claws and hiding their faces beneath masks or deep hoods. The most difficult thing for them is to rein in their hunger for combat, lest the glow of their eyes give them away.