At this point, yes for most classes on the base races (not allied). The reason why? It is because at this point each race would have seen the importance of each class, even if they try to make their own form.
Example, orcs see that those pesky humans have paladins that can be brutal warriors that also wield the light, and use it to strengthen and enhance themselves (ret). Then they realize that their best buddies, the tauren, have something similar in the form of Sunwalkers. So a few convert to the order of the sun, and train in it. They wouldnt be the same paladins as the alliance, and slightly different then their blood elf allies, but something that seems very logical.
Let's do another... draenai rogues... oh wait they exist in lore. Shit, what about warlocks... damn they exist too... wait... I can work this. Fire against fire type, yeaaaa. Seeing how the legion was crushed, some draenai begin using the powers that had been forbidden. Not because they seek power, but to learn to control it so it never happens to their race again. To seek out those traitors that do wish to see the legions return. Calling the powers of the defeated legion to bend to their will, now that they no longer need to hide (confidence and pride being there for a storyline). Hatred and subtle curiosity from their own race. Would be fun to play a proper hated outcast.
But you see... it works for every race and class. It doesnt matter. You can come up with some excuse as easy as one of these or far more complex. It doesnt take a genius of a tauren to see how sneaking around could be useful or an undead to realize the usefulness of the light to smite their foes