I have only played a Tauren Shaman, but i'm thinking a lot about what race i want to use when i start to multibox shamans.

My problem with Taurens is that they are very clickable. I get attacked no matter where i'm standing in the zerg express going do Vandar.
Sure, i get 5% more HP, but i don't think that makes up for it at all.
I have tried various effects to make the Tauren smaller, and that really helps with survivability.

I get CC'd to death a lot. Maybe i just suck, but i would think the stun resist Orcs get, coupled with that they are not as clickable helps a lot. I think i will start playing five orc shamans.