Vamp, the two dragons are level 50 elites and they are the objective of your quest. They spawn once the Earth Stone is activated, and if they're already there, it's because someone else activated the stone and got killed.
I'd find a few high level players to help you out. You can pull them individually as well, which makes the fight a bit easier than it looks. And the armor you get for doing this quest is totally worth the effort.