Actively raiding with Blizzard’s default UI is considered to be a hindrance the base game doesn’t include damage meters or a way to gauge your success, and you rely on in-game voice cues and animations for telegraphed abilities. Once you get up to Mythic, everyone needs to know the strategy and be ready to execute it. Even the Looking for Raid difficulty, which is meant to be conquerable by any player, requires some degree of coordination and effort. Raiding in World of Warcraft, no matter what level of difficulty you choose, is challenging.