After the next patch, 8 out of the 13 classes will be available to all races (except Dracthyr). The ones remaining are Druid, Shaman, Paladin, Demon Hunter, and Evoker. Out of these 5, I think Shaman would be the easiest one, from both a gameplay and lore perspective, to be extended to the other races. So I’m trying to come up with ways to make that work on lore.
General Ideas: Earthen Ring Emissaries travel to every city to teach the people there shamanism. It’s easy, but boring, and would lead to homogenization. Why would they travel to each city? Well, why not? Maybe they think the world needs more shaman. Honestly, nothing was stopping this from happening in Vanilla.
Or, each race that doesn’t have Shamans could just learn from the other races in their faction that do.
Race specific ideas:
Human: The elements in Westfall need someone to calm them down.
Night Elf: Well, in the Firelands Raid, Cenarius seemed familiar with the elements and how they work. Honestly surprised he didn’t teach them Shamanism by now.
Gnome: Using Machines to make contact with the elements.
Worgen: Um, there could have been some ancient Shamanic tradition we don’t know about in Gilneas.
Undead: Some sort of fungal druid, or they could simply learn from the Tauren.
Blood Elf: A questiline where they make peace with the Amani, and their loa teach them. This isn’t mine. This is Baal’s.
Void Elves: They could have Dark Shaman, but I’m not really a fan of Dark Shaman or their practices so idk.
Lightforged draenei: Same as the regular Draenei. The path of Shamanism is another facet of the Light, according to Nobundo.
Mechagnome: Same as the regular gnomes.
Nightborne: Some sort of Arcane Shamanism.
These ideas are rough and probably not great, so feel free to share your own.