I did that too. I got hit by something (I don't know what) about halfway through, and it took my health down really low, but otherwise it was a pretty boring fight. Maybe it's better with other people, or a different class (I used Roland).
Also, it would have been nice to actually get into the vault (*gasp* spoiler!). At least they could have shown the character wandering in with light shining on his face before it fades to white or something...