M’uru wasn’t even the most creative boss in Sunwell in terms of mechanics, but he single handidly destroyed more progression guilds than any other boss in WoW history. Why? Because the tuning was absolutely brutal and left no room for mistakes, lag or even indecision.
One of the guilds which got US top 10 kills on Kalecgos and Brutallis and US top 20 on Felmyst took almost two months to kill M’uru.
Anyone who scoffs at how hard M’uru actually was is either from the original 5 ultra-elite guilds who downed the 1.0 version, from Drow, who had that amazing AoE strat that everyone else tried but couldn’t replicate, or simply didn’t raid Sunwell pre-3.0. Everyone else struggled with him, and most struggled for weeks and weeks.