I have been mulling this issue for the past few days based in part on my exchanges with a few people on these forums, and I feel like there is one particular issue that sometimes goes unnoticed, yet is fairly significant in how the writers structure the narrative - whether they are aware of it or not. That issue, as you may have guessed from the title, is that a large part of the problem with writing the faction conflict is that the Horde has become too weak to properly tell the story. Not only does it make the Horde story frustrating, but it also makes the Alliance story frustrating because they have to be artificially hamstrung in order to keep the narrative going.
I have heard a lot of “Where is the Vindicaar?” “Where is Jaina/Alleria?” and so on. These are good questions, and it’s not as if Jaina or Alleria are somehow combat-averse, but the problem is that they have been elevated in power to such levels that we, the players, rightfully expect them to be walking forces of destruction - and that’s a problem. It’s not a problem necessarily because of power creep (although I have my own reservations about that), but it’s because the Horde has been given no means to reasonably counter their power. Likewise for the Vindicaar, and so in order to even have the semblance of an epic war between world powers, one side has to hold back lest the other be defeated immediately. This isn’t even to mention the fact that Horde weakness is pretty clear even in their own story, and rankles more than a few players in its own right.
A weak Horde is a Horde that must resort to atrocities and superweapons to fight, because they are given no other means to achieve any kind of parity. I would guess that everyone, even Forsaken fans, is probably tired of seeing the Blight at this point, but because all of the Horde’s other military forces and notable weapons have been torn down or just not developed, it’s rapidly devolved into a one-trick pony. The Horde being the faction of atrocities and superweapons is fun for almost nobody. It’s not fun for Horde players who dislike feeling like villains in their own story. It’s not fun for Alliance players who are unable to stop these superweapons, because doing so would instantly rob the Horde of any semblance of military parity and thus make the story collapse in on itself. A Horde that can’t fight back on even terms is a Horde that can’t be attacked full-force by the Alliance. Fracturing the Horde just exacerbates this problem, as a Horde that is fighting itself shouldn’t be expected to be able to fight back against a unified foe.
To wit, these factors make the story predictable. The Horde sounds one-note villain drums as they hit the same tactics over and over again, increasingly featuring the same races and characters over and over again. Disunity prevents the Horde from developing enough strength to fight the Alliance on even terms. So the Alliance has to pull its punches. The development of other characters is now essentially on hold while the civil war narrative sucks all the oxygen out of the story. The Alliance is portrayed as very close to winning in 8.1 - but because we know the Horde is incapable of fighting back, that limits the directions the story can go. Either an atrocity brings them back in the game (Derek) or a third party strikes a blow instead (Naga), and it leads to a very unsatisfying experience for everyone. That, or painfully obvious plot armor allows a Horde counterattack to succeed somewhere when the deck is stacked against them.
A stronger Horde may not necessarily produce more satisfying conclusions - nobody is going to win, because that’s how the faction war works. But when the Horde is weak and incapable of dealing with the Alliance’s vast array of weapons, it causes the story to distort around the “there must always be two factions” bit, rather than that theme being maintained in a more logical sense of two superpowers unable to strike the killing blow against each other.