Not everything in the game is supposed to be balanced.
No reason why it shouldn't be.
Breath weapons IIRC were primarily an ability that NPCs used too.
In the Books, sure, that's only because Dresden is a Wizard and didn't have any friends with a breath weapon. There are plenty of ways that players can have access to them.
Consider: A PC with high weapons, a stunt to use anything they pick up as a weapon, and breath weapon would basically never be without a weapon they could use to deadly effect. Additionally, they'd be able to deal with opponents up close and farther away without missing a step.
My reading of the rules is that someone with high weapons doesn't need any stunt that lets them use anything as a weapon. They already can do that. They can pick up a chair and use it as a weapon, if strong enough. If strong enough, they can pick up a chair and THROW it as a weapon. They could pick up a couch and throw it as a weapon. If they get a lift of 15, they can pick up a CAR and throw it (doable with Supernatural Strength, Hulking Size, Might 5, and Mighty Thews...or you could have Mythic Strength and rearrange things a bit..well, 14 is technically good enough for a small car). So again, someone with Inhuman Strength already has a breath weapon since they can toss baseballs (weapon 0, I'm saying, +2 for IS). Easy for them to carry a bag of baseballs (and I'm talking about 100 or so baseballs here), and they can basically have it all the time. If they get captured, the bag gets taken away. If someone with a breath weapon gets captured, they get muzzled or otherwise constrained so that they can't use it. Pretty much the same thing. If they have Supernatural Strength or better, then the bag of baseballs or anything they can grab in the environment, is far better than a breath weapon.
Overall, Breath Weapon is questionable enough as a 2 refresh ability. Not having it scale with Strength powers makes it pretty much a joke for any strong character who can literally grab anything near them and throw it to better effect.