Sure, we could just keep on going but wouldn't it be more a lot more forgiving if we had something to counter the 'oh-shi' moments? It doesn't necessarily have to relate to personal fails - I'm talking about unavoidable raid damage as a whole. So for example, if a RL could choose between an anh shaman or a hunter, and he/she is in this position where the raid's health just seems to be spiking too much and we're losing people, who would he/she choose?
Baring in mind that both players are equally as geared, skilled, have the encounter experience and deal a similar amount of DPS. We could even say they're very likable and friendly if you want to put it that way too. Who would you take? I'd obviously choose the enh shaman in these circumstances. Again, you could argue that it should still work with the Hunter, and that it would still be doable with the Hunter, but just how long will you keep trying when you already have a rough idea of where the problem lies?