Dragon Breath damage is based on current HP, and victim's Fire Resist. For pets Dragon Breath appears to have a 18 sec CD, while players using Ninjitsu's Reptalon Form (from Talisman of the Fey) can spam Dragon Breath by repeatedly going in and out of War Mode while double clicking on the target. I wish there was a Dragon Helm Artifact that gave the player the Dragon Breath ability like Reptalon Form gives.