To be fair, most of those can be accomplished by a 2nd War DK who decided to go a bit more Dark Shaman(Dominating Decay, rather than Harmonious Spirit like normal Shaman) than full on Warlock. Because binding the souls of the dead is literally how they're made. Shove a Warlock's soul into a dead Alliance hero to use the soul of the Alliance hero as a power supply. Involving Elementals in their magic, which can be extremely forceful and corruptive
without Fel magic through what's justifiably called Decay, could confer the "living" feeling to their magic, as Elemental forces have a pretty shocking habit of becoming actually alive when concentrated. Just ask the Stormstouts, who accidentally made booze elementals. One of which was a dungeon boss made by attempting to attain enlightenment by perfect booze. I wish I was joking, Pandaria has weird stuff like that all over the place.
To be fair, the "better" you describe was basically the case for the 2nd War Death Knights, who had more of a field commander role than even the 3rd War DKs. They even have the ability to be brought back at least decades after "death," like WHFB Vampires (seriously, the blood sucking buggers have actually been "dead" for
centuries and came back. They're basically impossible to
keep dead short of direct soul destruction).
I brought up Nature/Void magic mixes as an example of how mixed types of magic change properties. The Emerald Nightmare offers abilities only tangentially related to the Emerald Dream, with the resemblance being pretty hard to find. Similarly, mixing stuff with Fel magic in a manner similar to how Necromancy in Warhammer Fantasy works could result in very different properties.
Actually not nearly as large as it seems, if you mix and adjust the right lore. One of the big things is that all the "civilized" magic users descend from a single tradition. Probably Troll in origin, related to Voodoo's tendency to mix literally everything able to be found, because the Elves of Warcraft are descended from a specific group of Trolls. Specifically, the Highborn established the tradition as it stands currently, while the War of the Ancients eventually led to the surviving, exiled Highborn becoming the High Elves. The High Elves, much like Warhammer Fantasy, were the ones who taught humanity how to use magic, and this extended to Dwarves, Gnomes and basically everyone that didn't have a previous tradition for it, like Trolls. Even the freaking Kobolds and Gnolls use self-taught variants of that tradition.
Something I've seen in several fanfics that might be drawn from the RPG books (it has to be from some canon source, the writers are too spread out and Warcraft fanfiction isn't as degenerate and self-referential as
popular storytelling series. People play WoW to RP and grind, rarely for the story) is that Arcane magic is "purified" Fel magic, and this is what the Elves know. Ordering the corruptive mess into safe to use energy that can be used for a wide variety of tasks. Rather similar to High Magic and Dhar, only in this case it's more like extracting the stuff of the Winds from Dhar, then casting High Magic off of that. Something that only the Slann should even be
attempting to pull off, but this is Warcraft, not Warhammer, so stuff like that gets some degree of a pass. Light magic is drawn from some omnipresent field, rather than any sort of current. Druidic magic, canonically, is from the Emerald Dream, which had its last canonical origin (to my knowledge) being "artificially shaped dreams of the world-soul of Azeroth." Fel magic is drawn raw from the Twisting Nether, and sometimes generated by self-sacrifice of a rather corrupting variety. Or sacrificing others, the blood rituals don't care if it's you or some poor sod you strapped to a ritual slab.
Once you divorce the relevant forms of magic to the native's interests (Fel and Arcane) from what swapping Leylines for Winds causes, you can have your direct counterpart setup work with little issue. You also have to somewhat divorce the idea of Winds of magic from a specific origin point, but the magical typing works for all the Winds if you have them be based on the dominant magical association. The only Wind that
should be relevant is Shyish, the Wind of Death. I'd counterpart it with Decay, with "sources" being heavily Sha-tainted portions of Pandaria(disharmony among Elementals is a symptom of Decay presence. Azeroth's general inter-Element hostilities are from a Spirit deficiency because the world soul is eating up all the spare Spirit) and places where unquiet dead lie/walk/generally do mad science(WTF, Royal Apothecary Society? You had
one job, and did the
exact opposite with your Blight!)/live semi-normal lives. Like most of Lordaeron, so you wouldn't have
any issues with access while in Forsaken territory
Using Leyline-derrived magic to act as a buffer for Fel magic is nothing particularly revolutionary, conceptually. After all, Trolls mix literally every form of magic in the world they have access to into a single form of use that requires their regenerative blessings to survive use of in the long run, or even short term, and they suffer no characteristically ill effects(no tentacles or mad ravings, just severe body strain) from the Void magic involved(and there
is Void Magic, their ancestry goes back to Old God domination of Azeroth, so they can and will use it). And probably Fel, too, they've had the whole time since the War of the Ancients to get that in their mess of a discipline they call Voodoo.
