These are Year One Values. Dragon's Breath now has a year two version.
Excerpt from "'Should I Buy It?' – Dragon's Breath & Other Exotics"
Dragon's Breath is one of 3 Exotic Rocket Launchers, unique for being an "Area Denial" weapon. In the wake of its blast, DB leaves a Solar Flare – just like the Sunsinger's Solar Grenade. Dragon's Breath is in the highest Blast Radius tier with average stats compared to its peers. The talent Javelin improves its Velocity and makes it a well-rounded Rocket Launcher.
Dragon's Breath is useful if your specific goal is to deny/force movement. The problem? That's a defensive maneuver for a very offensive type of weapon. If you're laying down a rocket, you might prefer its just destroys everything. If your targets weren't in the blast radius, they're probably not going to waltz into the Solar Flare. Again, if control is the goal: great! Otherwise, you might look to another Exotic to get the job done.
PVE: Some Guardians say the Solar Flare is useful against low-mobility bosses, as they won't avoid the flare.
PVP: Dragon's Breath might get occasional use in Control where denied/forced movement is extra helpful.
(Another good Exotic Heavy for area denial? Super Good Advice.)