A couple things to note. I have the lightning spell that can disintegrate enemies. I ended up disintegrating the 2nd guy, so i couldnt complete the mission. the other 2 would just stair at the coffin behind them and nothing would happen.
Also, try not to stand near the doorway where the gate comes down so you cant leave during the fight. I was shouted into the gate, my legs got stuck. Then another shout hit me and I went through the gate and couldnt get back in.
Good thing I had the game saved right before the fight started.