Personally, I feel they need more than just a dragonbreath. Back in 4e, it was only one part of their race, now here it's pretty much all they have. This idea improves their breath, but then makes you get a feat to get things that probably should have been there from the start.
4e, you had the following...
+2 STR or CON, +2 CHA
+2 History, +2 Intimidate
+1 attack when bloodied (hitpoints at 1/2 or less of max)
+CON bonus to healing surges
Dragonbreath of, well... I'll link it. http://dnd4.wikia.com/wiki/Dragon_breath
In 5e, you have...
+2 STR, +1 CHA
Dragonbreath based on draconic heritage
Resistance to element of dragonbreath.
...gee, that's a big lack of stuff between versions, huh? I feel like 5e misses the point of the dragonborn. You aren't just a guy who can breathe fire, you're an unstoppable force of draconic might who can scare his adversaries if you so wish. Then sit down and teach your children, who you were so rudely interrupted from, about your clan.
A stronger breath, unfortunately, doesn't fix that issue.
I'd like to propose trying to bring them back to that proud, fierce, yet knowledgeable warrior type that they once were. Though, not too sure on how to go about that, as is.