While that's a legitimate strategy, it's also incredibly defensive. What happens when the bard chooses to leave that scenario and the Shaman must chase if it wants a kill?
It also assumes the Shaman can deal enough melee damage to take the bard down. If no silence, the bard can just flee and be full hp/mana/move unless there is a ton of pressure being put on.
Meanwhile, that bard will be pummeling the Shaman. I'm not saying it can't be done. Just in theory it seems really, really disproportionally in favor of the Bard. I would love to see a log of a fight between the two.
Also, I'm not saying this is a bad thing. Every class should fit somewhere in that rock paper scissor scenario. I'm still figuring where bards belong in that.