I finally beat Aria's unique final boss! I think it's too hard, personally. Aria already has enough to deal with when you factor in her low capped HP and penalty for missing a beat, so the boss room having two sarcophagi, the boss inflicting confusion, and the boss eventually summoning dragons are all a bit much. I think if one of those three things were trimmed this boss would be just perfect.
That having been said, Necrodancer is an incredibly good game and I recommend it to everyone. I put it in my "Hall of Fame" Steam category.