Dungeon is fine. Dungeons in general have needed some amount of teeth for the last decade. This hits that spot that I feel they've always needed.

Alex's first boss still has "simple mechanics" but they do need some reaction and "monkey see monkey do." The game doesn't always have to be effortless. By level 100 people really need to start grasping the basics of the game or ask for help. If you wipe, learn what went wrong and try again (it's JUST stack/spread, donut aoe, and cross aoe + tentacle, it even shows you and in what order!).