I consider the unupped to be balanced.
Yes and no. The unupped dragon makes a terrible catapult target with its current hp. I'd like to see the unupped dragon with 25 hp like armagio. As is unupped dragon is a terrible attacker, terrible catapult target and terrible gravity pull target. Higher hp fixes the last 2 for the most part.
Without gining the dragon an effect or reducing its cost, there is really no other way to improve it. It needs 1 less attack than Basalt, which itself is somewhat weak, and it will always be 3rd in pecking order of catapult targets unless it gets like 40 hp since armagio is strictly better.
With the unupped I view it as card advantage vs cost/attack efficiency when compared to the other Gravity attacker Sapphire Charger
10
+2cards = 8 Momuntum attack with 5hp+5hp resilience
10
+1card = 7 normal attack with 15hp resilience
This is close enough to balanced in my opinion that decks with fewer card slots available for win condition cards would select the dragon over the charger and vice versa.
The same argument is not nearly as close using the current Massive dragon
10
+2cards = 14 Momuntum attack with 5hp+5hp resilience
Now: 11
+1card = 7 normal damage with 30hp resilience
My idea: 9
+1card = 8 normal damage with 15hp resilience
I admit that upgraded my idea still loses some ground when upgraded compared to the charger but I think it would still have a niche in decks with very few slots for win conditions.
Of course you also point out the other solution (make it the king of catapult fodder)