I think the big thing that you’re missing in your argument is that as long as factions continue in their current form, the situation will not get any better. If you go by simple numbers in the blandest sense, “Horde” are not underrepresented through characters in the story that we see. It’s just that the “Horde” representatives we get since Legion have overwhelmingly leaned on dead humans and pretty humans with long ears. Because hey, that’s the easy way out. And this problem has its roots in the fact that Blood Elves were conceived of and added to the story as nothing but a transparent attempt to bring Alliance players to the Horde to balance the numbers.
Blood Elves on paper, sure, they reinforced the narrative of the Horde as outcasts and renegades pre-Sunwell. They didn’t even escape their expansion with their themes intact and absolutely no thematic quality control on quest writing has done a number on them (as with everyone else).
And then the WC2 contingent in the writing staff defined the “Old Horde” as nothing more than “the guys who start crap” and there you go, that’s the majority of Horde writing besides Zandalari.
I agree the situation looks bleak for the Horde going forward with the cosmic focus, but I’m willing to bet a lot of that got a handwave on the basis of “oh, the Blood Elves are all about the Light and Arcane and also I guess the fel and they’re the majority of the Horde player base”. In much the same way covenants probably got a degree of handwaving because of Maldraxxus for the Forsaken and Revendreth for the Blood Elves – there are themes related to major groups in the Horde, after all!
Centralized class orders did a better job of getting close to faction parity in theming than every phase of the game except BFA, which I’d argue was mostly forced by the fact that they’d had vague plans and build up for the Zandalari for over a decade – there’s nothing left to mine there. And you’re not wrong about them being Alliance-dominated, but having the four classes you pointed to (and I think Hunter did an OK job within the constraints of ‘why the hell would people who shoot animals get together as an association to stop demons’) still forced them to focus on more themes than they usually do.
I primarily play Alliance now because I haven’t felt like there’s been anything of the launch Horde I loved a long time ago and the forced binary was making it worse. Gnomes have it pretty good. We’re practically the only race that delivers on what most of us roll them for: we are cute, slightly deranged, fourth-wall tapping westerner human variations that can occasionally be badass, which is the only thing Blizzard as a company will consistently write.