Miraak was good enemy, but too weak and easy to beat.
1. Ebony warrior, karstaag,
2.alduin and dragon priests
they was much thougher than Miraak. I hope we see much thougher enemys in future skyrim.
1. Ebony Warrior and Karstaag were more like secret/bonus bosses and are purposely made far more powerful than they canonically should be. It was just something Bethesda added to challenge high level players.
2. To each his own, but I'd say Miraak was far more dangerous than Alduin or a dragon priest.
I do agree that he should've been tougher.
OT: I liked Miraak as a character. He could've had a more direct role for sure, but overall, he was among my favorites. Much of his background was left ambiguous because it was his background. Not yours. We know all about the Nerevarine's background because he got his own game. But if he were to appear in Skyrim, our character would learn little about him. I think the devs wanted Miraak to be like a corrupted mirror image of the pc, that's why they gave him a background that was just as open as our own.