cant do damage to a pally thats bubbled .
use it to close distance and youre able to do damage just fine in melee range.
cant even be affected by earthbind or frost shock while bubbled.
but i can say you do have a point with multiple of the same class compounding and getting rid of the classes weaknesses.
can say that for a bunch of classes though but i understand the logic of having multiple shamans being a problem.