It took us about a hour to figure out enough of the mechanics to kill Enraged Sephotep. When we killed him, we were still trying to figure out exactly what was bringing his shield down in each of the phases, and as you can see from the video it took us a while to bring down his last shield since we weren't totally sure what was causing it to go down. Enraged Sephotep was definitely the most difficult boss in the Citadel raid.