ZeniMax also emphasizes the importance of testing for these dungeons:
Much like we do for Trials, we have groups of skilled, coordinated testers ready to take them on. The Dungeon Team wants to kill you, don't get them wrong, but they don't want bosses to be unfair or impossible. It's a difficult tuning and balancing act to get them just right, especially considering the broad range of character builds that will be attempting them. When the testers wipe several times learning the fight and let out a cheer when they finally manage to scrape by with a win, we know we're on the right track.The video that accompanies the post is embedded below.