To be honest, in my mind it's pretty clear this was meant to just be a fun glyph. "Slot the glyph for a night and tank an instance for your buddies!"
They certainly could make it a proper tank spec, and I don't see anything wrong with that idea, but I'd guess Blizzard doesn't want to try an adjust around yet another tank when they are already adding a fifth tank to the game.
And honestly, if they did want to do this, they should give it to Enhancement shaman; they at least had tank-lite abilities in classic.
Dovie'andi se tovya sagain - it's time to roll the dice