I will prove by logic that there are no good arguments against the Demon Hunter as class, for a new expansion.
Let's start with one very popular.
"Demon Hunter and Warlock can't coexist because Warlock already have Metamorphosis."
Tyrael strikes back!
These are all examples of why there is reasonable doubt that the class can't exist.
- Before the pinnacle of evolution, Demon Hunters could not unleash the demon in them and turn themselves (temporarily) into something more, called Metamorphosis.
- Demon Hunters have been purged off their demonic being, they are now Demon Hunters without the demon in them.
- Demon Hunter class is about the hunt for demons, not to become a demon. Diablo 3, Demon Hunter does not become a demon.
What I am saying is not unreasonable, it is imagination, anything can happen with magical powers in a world as big as World of Warcraft.
So feel free to give you're good arguments and if they are good, I'll strike back at you with mighty force of logic to prove you wrong.
All that I am proving is that, as long as there is reasonable doubt that the class must have Metamorphosis to exist, it's fair to believe that the class can exist in World of Warcraft without a demon form, when game developers create lore for it.