This dino lacks any real utility due to the fact that it is a boss and therefore cannot be tamed.... But it drops the highest amount of element out of the four bosses if that can be seen as a utility of sorts
FYI the fire damage is percent of health based, its not reduced by armor or levelling health. In fact, the lower the health the better tbh. Because if you have a massive health pool your pig will struggle with all the health to recover, while if you only level melee the damage done by the fire can be more easily dealt with, and youre less likely to lose rexes/therizins.
For most of the players, the dragon is a boss that you fight by spawning it. For the rest of them, i.e. the ones that play Ark: Survival of the Fittest, have the dragon available for a short amount of time and able to be ridden, then it will turn it's back on you.