LFDraenei definitely should have got Monks. And even Shaman, considering some link between shamanism and the Light has been there since Rise of the Horde. ('Member how the orcs shamanic offerings of prayers and water helped keep K’ure alive and prevented it from going void? Anyone? Bueller?)
Other AR class missteps:
Highmountain Paladins and Priests. They have a literal “Path of An’she”, there were AP items and artifact relics named after An’she, they say “An’she guide you.” The lore of Sunwalkers and Seers tells us that, through learning from Kaldorei, the Kalimdor Tauren began to over-emphasize Mu’sha at the expense of An’she, but there’s no reason to suggest the same thing ever happened in Highmountain. Fact is, Highmountain worship An’she and never stopped. Then with Priests, you’ve got the whole spiritwalker and void thing going on, not to mention the kobold quest. Missed opportunity big time.
Highmountain Warlocks. I can think of nothing more quintessentially tauren then allowing their lost Bloodtotem brothers to repent and use their newfound powers for good.
Zandalari Warlocks. There’s literally one in-game. They have lore going back to Vanilla. C’mon Blizzard.
Kul’Tiran Paladin. In Warcraft 1, 2, and 3, ALL HUMANS WORSHIPED THE LIGHT. Now, that’s not to say I don’t absolutely love harvest witches and Tidesages and all that good stuff. It’s great. It’s awesome. Making Human societies religiously pluralistic with competing cults is even awesomer. Keep the Light in Kul’Tiras, heck, make it a minority faith if you want. Give us Kul’Tiran (and Worgen) Paladin.
Zandalari, Kul’Tiran, Mag’har, Dark Iron DK. Mercenaries who signed up with the Argent Dawn, just like all the other DK races. Dark Iron are Thorium Brotherhood initially, Mag’har would canonically be MU Mag’har who came over with Garrosh. We didn’t see them because they returned to their respective peoples, not to the Alliance and Horde.
Thanks for coming to my TED Talk.