Originally Posted by
Soulwind
The Twisting Nether, as chaotic as it is does seem to follow some rules (that's why warlocks can summon things from it, taught by other warlocks). Even if space isn't just space in Warcraft and worlds are connected in unpredictable, magic ways, time and reality appear static.
So yes, an alternate universe has an alternate Twisting Nether with alternate versions of the same demons. If this was Marvel and not Blizzard, we'd end up fighting against two Sargeras at the same time.
Thankfully, the writers realize that this is a) bad writing and b) confusing as hell, and don't plan to expand much on the concept. If anything, they prefer CoT-style timetravel with the usual Back to the Future rules. They just needed an excuse to borrow some dead characters from this universe without consequences so that future linear stories in our universe can have them.
I personally don't hate the idea of alternate characters. An evil Thrall, a good Neltharion... anyone really can be introduced in a different way while keeping the familiarity. I'd just wish they skipped the part where we visit their worlds and simply brought them to ours, like the ones Kairoz summons in the novel. A cinematic, a few quests, some short stories... they're all they'd need to introduce some alternate/past/future characters, and we wouldn't have to deal with the rest.