I actually think it’s the opposite.
The Alliance has a mantra, but very poor character development. The Alliance kind of falls on the back end of a story that is primarily driven by the Horde. Often times, forced to acting against their own self interest for the sake of the narrative and gameplay limitations. Not to mention the Alliance “mantra” can also be contradictory to the various races that inhabit the Alliance. The Alliance “fee” is basically Male Human Paladin fantasy heroism. It is very “The Knight who slew the Dragon” type of characterization. Which is sort of contradictory to the Savage Woodland Amazons that are Night Elves. Who back in WC3, were portrayed as very aggressive and uncompromising and intolerant of trespassers and outsiders in general. If anything, their interpretation of the Knight and the Dragon story would be a tragedy and an act of barbarism, rather than an act of heroism.
The Horde has a different problem. The mantra of the Horde is not properly defined. Sure, they have “Lok’tar Ogar! Victory or Death!” But that’s kind of shot them in foot. So far, it has been more death than victory except for the instances in which they join with the Alliance.
It is easy to see why, if you have a faction who’s slogan is “Victory or Death” vs a faction of Knightly heroes and warrior priests, who would you suspect to be the aggressor? And in traditional fantasy, who would you suspect to be the “Good Guys”?
So the Horde is frequently the aggressors for this reason… Reason being that it’s easy to write. You don’t need much nuance, and with the assumption that your customer base are children or just very stupid, you don’t want a nuanced story (Which is the most frustrating to me, because it is obvious Blizzard thinks we are idiots).
As aggressors, Horde characters are often the catalysts of major storylines. Because of that, the Horde gets some pretty great character development, but that development typically ends with death. As such with Garrosh, Saurfang and technically Vol’jinn. We can assume such is also the case with Sylvanas.
I think the Horde needs to be revisited. Writers need to figure out what the Horde is and what they stand for beyond Lok’Tar Ogar. With the implementation of a ruling Council, the Horde might get that. I think also, the Alliance needs to be a catalyst of a story as well, and the trick is to do that without flippantly killing off characters like they did with the Horde.
I think a good way to do this is having Alliance characters dealing with corruption from within. Perhaps Flynn Fairwind, as he develops a friendlier bond with Shaw, discovers that Shaw has been withholding or fabricating valuable military intelligence. Perhaps protecting Vanessa Van Cleef, the daughter of his old Friend, who’s death he still feels guilty over? Or perhaps Shaw knew about the War of Thorns, but withheld it as a plot of the Uncrowned to dismantle the factions?
Idk, anything like that. Where Alliance characters come into moral conflicts, not because they are mustache twirling evil, but because they are flawed.