I know I’ve been advocating for night elves here, but I really think tauren are just currently very weak compared to any of the other races.
Sometime back, I was thinking they could use a counterpart to Elune, An’she, but I feel they do not have a common cultural connect to An’she as the druids do.
I remembered a scene back in Warcraft 3 where Cairne Bloodhoof- the warrior chieftain- channeled the Earth Mother and collapsed a ravine on incoming centaur:
Most people don’t recall this cutscene, but it clearly shows the power that tauren can wield by the entity the Earth Mother. All tauren revere the Earth Mother unlike An’she who gets more attention from druids, like Musha.
Cairne was no shaman, but all tauren have relations to the Earth and the Earth Mother. A shaman ability, reincarnation, also comes from the tauren chieftain. The tauren, even non-shaman, and especially the Chieftains, should be able to channel this more frequently and with more power like Cairne did. I don’t really like Baine, but I see him as being too weak and too cow-like, and maybe that can be fixed by elevating his power level to match that of Cairne.
The nature of the Earth Mother is somewhat a mystery- it is unclear if it is the eternal earth spirit or the titan Azeroth, and either would work, but I would prefer the earth element, because of its shamanic themes and the tauren would use more Earth powers which there is a dearth of in this setting. The earth element is also generally calmer and patient until provoked, something reminiscent of the tauren themselves.
Tldr, empower the tauren with their ties to the Earth Mother, to put them on par with other races, give them their own Earth mother mystery deity, and return them to their wc3 roots.