How hard is it for Blizzard to develop new dragon models?
What are you hoping for, exactly? It's a ******* dragon. Google it and you get one of two answers: the winged lizards from medival times (knights vs dragons) or the serpentine asian style dragons (think of Gyrados). The fact that proto drakes exist at all in the game is a step-up. They literally created something from nothing there. In all my time as a dragon fanatic (age 6 to today, so 16 years now), proto drakes were never even thought of, even as a side note of, "Hey what if dragons were like this?" Enjoy the dragons you can ride, dammit!
If you think the Bible is a strict set of rules, you're gonna have a bad time.