Actually it always kind of annoyed me, even (maybe especially) lorewise, I can't play every class on every race. How is it that a tauren is mentally incapable of becoming a mage? Or that goblins are able to convince the elements to obey them as shamans but can't convince nature spirits to let them become a druids?
Ok so maybe the general culture of the tauren doesn't involve a lot pure arcane magic. I can still see certain individuals (and taking the entire race quite a few individuals I'd say) be interested in it and pick up the trade from other races. Humans had to learn from Elfs in the start aswell. As for the favor based classes, that need favors from nature/elements/gods/etc. to get things done. I can imagine that those beings are capable of detecting if a person is made of the right stuff to be allowed the favor, no matter his race.
I never min/max my races tbh, I always pick what race I like at that time or fits my general idea for the character. I really love your idea of the racials talent tree though, would finally make me pay attention to them
Just call them heritage or something, being raised in the woods nets you +herba, growing up in a cold environment nets you frost res and so on. Sounds cool
. And min/maxxers can just fuck all that and pick the best for their playstyle without any lore beeded.
Some might be tricky though, like whisp form for a orc