It's been a while, so I can't remember. This came up over at WoW Insider, about the newness of the dance, perceived or actual, and the penalties of bad dancing. So to you I ask, Do you remember if a screw up on living bomb on Baron Geddon was a wipe? I know it was a big deal and definitely a major setback, but I don't recall it being an instant wipe. For some perspective on my perspective, I was doing this with people in mostly blues, with one guy loaded out in purples because he'd done MC before. So it's not as is we were significantly over or under-geared. Looking at the ability on wowhead, it says 3200 damage. Trivial these days, but if I recall, that would have been a pretty big hit back then. Maybe not quite an instant kill, but close enough that it could trigger a wipe if it lined up with his melee AoE or if someone important had a mana burn tick.
Beside the power of the failure, I'm wondering about the difficulty of the mechanic. I don't think it was very difficult, and certainly easier than more modern dances. We'd set a spot to run to, or multiple, since not everyone would have time to get there, or just generally tell people to get the hell away from the raid. If they moved away, even to the wrong spot (high ceiling ftl), they would only hurt themselves, and even then a quick priest with levitate and feathers could save them.
It helped that the fight didn't have too many things going on. Some classes were, of course, on dispel duty, because that mana burn would quickly ruin a caster, so a slight distraction there. Melee had to run out when he'd do his flame AoE. But overall that is two distractions, which would be almost exclusive, as there was only one melee class with a magic-remover, aka: lolret. When players only have to focus on that one part, it can be a lot easier to handle. It also helped that DPS was much simpler, leaving even more spare mental capacity.
So there's another aspect to consider, not just how difficulty a mechanic is in isolation along with the cost of failure, but add to those what is happening around the mechanic. If we're already worrying about X effect, when Y happens we may not be as ready for it, and will react more slowly and with greater confusion.