Tauren Heritage Armor Unlock Question

[Kaivax]

you only have to do the war campaign stuff (up and including “Stay of Execution”) on one toon on that faction, Tauren or not. Then of course, the Tauren you’re using for the unlock has to be at 120 and be exalted with Thunder Bluff.

This is correct. You can use your main character to finish the Campaign questline, and then switch over to your Tauren and start the Heritage Armor questline.