Gnomes need Demon Hunters.
I get that Elves are the most logical choice for Demon Hunters, BUT they are not the only race that should have access! Orcs, Draenei and Naga are all obvious choices, as are gnomes.
Let’s think back to Warcraft 3. Kael’thas is locked in the Violet Hold below Dalaran. Obviously he brought at least one gnome with him: Millhouse Manastorm. It makes the most sense. Millhouses wife is in the Violet Hold. My guess is that Kael meant to bring the more competent Manastorm spouse, and when he realized he’s gotten Millhouse, threw him back in jail.
But If Kael brought this one gnome, surly he brought others imprisoned in the Violet Hold. Gnomes (were) the only Alliance Race to practice the arts of the Warlock up until the Cataclysm. It would make sense that a number of these pragmatic gnomes would have been in the Violet Hold, and that Kael would have brought them with him to Outland.
Gnome Demon Hunter trainers could be more members of the Manastorm and Fizzlebang families.
It all makes sense to me!