You forgot the part where the Alliance consistently get their butts handed to them, and are made to look incompetent, weak, and cowardly. Portrayed as not being able to overcome their enemies unless saved by deus ex machina or the Horde turning in on itself. The Alliance player is made to feel weak, powerless, humiliated, in the promise that at some nebulous point in the future they’ll have their vengeance, but it never comes because the conclusion is botched in some way.
I think you are vastly overstating the “Alliance go here to kill Horde NPCs that the Horde aren’t aware of” because in my experience playing both sides this doesn’t happen all that often, but does happen often in the reverse. I mean, there’s an outpost of Sentinels in Ashenvale that you wipe out literally because some Orc guy and his two friends are bored as a prime example.
I’m not saying that Horde don’t also get a bad deal in the faction war. But a key factor in what makes Alliance players dissatisfied with faction war is what I’ve said above. Alliance players used to constantly call out for vengeance because the game never felt like it gave any proper resolution. It took 5 IRL years to get the NE hobos out of Stormwind, and 13 to get the Worgen’s home back.