As much as I hate the idea of a tank shaman, I do have to admit, it fits them.
They are the spiritual leaders of their people. They’re supposed to be the ones leading and guiding their people, especially in troubling times.
Makes sense they’d be the first to lead their people into a battle… asking the elements for help/protection, not only for themselves, but for the people they’re trying to protect
OG Blizz devs have actually flat out stated that they were toying with the idea of Enh being a tank spec. That’s why original Enh had so much threat generation and personal defensive cds built into a bunch of spells. Then somewhere along development they were like, “nevermind” and kinda made them a melee dps who could off-tank pretty decently until the complete spell rework in Cata.