I mean... If you're running through Molten Core, then I could see that being boring unless you were an expert commentator and could somehow keep the audience entertained; but if you're running other stuff like all of TK, BT, SW, Ulduar, ToC, ICC, RS, and the like... then that's a different story.
Particularly for me, watching someone just zerg something and completely overpower it isn't as exciting as say, watching someone do an encounter the correct way and having to move characters around to deal with the mechanics of the fight.
Connect With Us