I might be mistaken, but dropping a totem itself causes no aggro. When the tank pulls 3 mobs, and has only hit 1, the other two are on him simply because he's there. He has done nothing, has zero threat (though not for long, as any rage he gets will build threat). You drop a totem, you also have zero threat, but you've done something - so they come to you. It's similar to buffing, zero threat but you've done something and so you can pull aggro (oh the fun of Maulgar pulls when the pally throws BoS on me before tanks have their targets). In practical terms, no difference from what you've said, but there's still a difference :P