Well, I will give you the dungeons. I absolutely hate that Blizzard does this, but they do it because there's demand due to nostalgia there. But I hate it and I don't do them.
Rag though was a different thing... he was back in a new, forward-progressed story and you fight him in his realm. Fairly epic, I might add.
So does that mean we should never see Darth Malgus in future TOR expansions then, or would you considered that "re-hashed"?