You don't necessarily have to be the master of your class (or even particularly good) to buff another player so they can do their job better. Furthermore, if you bring a buff that doesn't scale with gear, why would I bother gearing you up in my raids? If you're going to complain about it, I'll just get another shaman who won't moan about how their ability to press a single button is carrying the raid. This is like saying the waterboy who kept the quarterback hydrated is what really won the game.
And yet I remember stacking nothing but warlocks and ENH Shamans for sunwell progression. No that was not fun either.