How about this tweak?
Crested Dragon
Huge Dragon
HP 120
Traits
Destructive Ferocity: The crested dragon has 2d12 of combat superiority dice, which refresh at the end of its turn. It can spend these dice to add damage to its attacks. Additionally, it can spend dice as follows:
- Batter. Spend 1 die to make a claw attack.
- Devour. Spend 2 dice to make a bite attack against a Medium or smaller creature already grabbed by the dragon's bite. On a hit, the creature is killed.
- Fling. Spend 1 die to make a ranged attack with a Medium or smaller creature already grabbed by its bite or claws, at a range of 10/50. It makes an attack, +5 to-hit, 1d12 to both the thrown creature and the target.
- Knockback. Spend 1 die to knock back 10 feet a creature it strikes with its claws.
- Snatch. Spend 1 die to grab a creature it strikes with either bite or claw.
Impenetrable Hide: Whenever the crested dragon would take damage, prevent 10 points of that damage. If an attack critically hits the dragon and manages to deal any damage to it, the attack creates a chink in the monster's armor, and it loses this resistance.
On its turn, if the dragon is in its hoard it can choose not to move. Instead it can roll in the treasure and fill the weak spot in, regaining this resistance.
Claw: +5 to hit (reach 10 ft), 1d8+6 damage.
Bite: +5 to hit (reach 10 ft), 2d6+6 damage.
Tail: +3 to hit (reach 15 ft), targeting up to three adjacent creatures within range, 1d6+3 damage.
Spit Fire: +3 to hit (range 50/150), 1d10+4 fire damage.
Breathe Fire: The dragon breathes fire in a 30 foot cone. Any creature in the area takes 3d10 fire damage and catch on fire, taking ongoing 5 fire damage. They can attempt a Dex save (DC 13) to reduce the damage by half and not catch on fire.
Additionally, the area the dragon breathed on becomes superheated. Until the end of the dragon's next turn, any creature that ends its turn in that space takes 5 fire damage. Flammable unattended objects in the area automatically catch on fire and burn normally.
After using this attack, the dragon cannot breathe fire again for 3 rounds.