Here is a look at my backstory for Gnomish Illidari Forces and my own backstory. The explanations I use in here explain how goblin and gnome demon hunters could very well be possible even with the current lore and implications. Here is basically a summary of the reasons why and how:
1. Faction Affiliation issues.
Not apart of the Illidan’s Illidari(Dispite the name), but rather a secretive independent organization that was founded for the purpose of developing technologies for the purpose of fighting the legion.
2. Solving the “Its too dangerous for other races”, argument.
Instead of absorbing demon souls into their body, they use technology. It is known in lore than demon souls can be stored and harvested for use in technological constructs. The storyline can be argued that doing it this way is far safer, but not without risks.
3. " Why would their be any need for demon hunters anymore? The legion is defeated. "
Countless worlds remain conquered by the legion and are still seething with demons. There is always the possibility that someone very powerful among those worlds may try to arise and unite the legion once again. Demons can also come in many forms and the purpose of demon hunters was not just to hunt demons, but to protect Azeroth. Whatever presents itself as the biggest threat is what they go after next.
“ There was never any mention of a group like this in lore. How can something like this actually be taken seriously in RP ”
A: We know that both goblins and gnomes can be warlocks. This means that some of them can tolerate what it takes to deal with fel magic. This also means that people out there can use darker and more forbidden magics for the greater good. Though it doesn’t technically exist in lore, it is canonically possible it could if blizzard wanted to make it so.
So this basically explains an open area that blizzard could make demon hunters open to goblins and gnomes if they wanted to. Now this next thing may come as a bit of a shocker. As much as I would love playable goblins and gnome demon hunters, I would much rather blizzard come out with a tinker class for them instead. It would also be nice if blizzard expands on some of the classes. Such as maybe goblin/gnome monks and or druids. Paladin is also highly requested.
You see here is the thing. It is already possible to look almost exactly like what a goblin or gnome DH would be like with the right mog, toy items and in game abilities. You’d be shockingly surprised how close to a similar experience playing outlaw rogue in the right way can really make one feel like they are playing an actual DH.
PS: Lets also not forget to love the other short race of this game. Goblins would look pretty amazing as DH too. If I get the glaives on my goblin, you may see a goblin DH around here sometime.