I agree with Dark Dragoon. The bosses stay the same level regardless of what level you happen to be. As an example, I took on Lenus WAY before I was qualified to, and she kicked my butt. I got frustrated, and leveled up until I could not stand it any more (i am a very patient person). I then took on Lenus again, and when we were done fighting, all that was left of her was a fine red mist. I don't think that I even finished my original Dragoon Special before she expired.