I think it would make tank more fun if all your abilities were different when you were in one stance or another, or not in tank stance if they were to get rid of dps stance. For instance when you're in tank stance you generate enmity, your defensive abilities mitigate damage, etc, etc. But when you are in tank stance or normal stance you no longer generate extra enmity, your defensive abilities now do dps abilities. For example your shield wall or shield block abilities make your shield swipe do more damage or have no cool down or something. This is just paladin example tho. I think it would give tanks more stuff to do during off tank, but making your tanking stance more important cause you couldn't keep hate outside of tank stance.