Remathilis
Legend
Its worth considering that not all dragonborn breath weapons are equal. Even PC dragonborn breath weapons rank up with level, so its not unreasonable that NPC dragonborn could have weaker breath weapons and less frequent uses. Perhaps the basic warrior NPC dragonborn only does 1d6 or 1d8 damage (DC 10) once per day. A dragonborn commoner's breath weapon is a line that does 1d4 damage (DC 10), while something like a veteran dragonborn does 1d10 (DC 12) and recharges on a 6 on 1d6. As long as the breath weapon does not excede its maximum damage per round with its normal attacks, it shouldn't be a concern.Wut!? Not even PC species are well balanced. They certainly ain’t balanced for NPCs. I’m pretty sure AoE breath weapons that do more than enough damage to kill several enemy troops at once even if they are save beat a unit of dwarves with an extra hp apiece and the ability to sense tremors.
I believe if you use CR calculations using the guidance in the 2014 DMG giving the basic warrior Dragonborn breath weapon pushes its CR up from 1/4 to over 1. This does not happen for other species abilities.
(Its also important to remember that you don't have to account for all PC traits a species gets, just enough of them to give the feel of the species. If WotC has taught me anything, even if a species is considered a member of a given species, it doesn't mean it has all that species's traits).