Personally, I believe that the division of the players into factions is an obstacle to Blizzard's writers following through on their commitment to revitalizing the Alliance in a form that speaks to players who are looking at the Alliance as an assortment of symbols and meanings from the RTS games to today. It started with the partially aborted High King plot point. Blizzard looked at how the Horde players cheered "For the Horde" like a sports team slogan and tended to put their identity as Horde before their characters' races (a lot of most vehemently pro-Horde players I've seen are Forsaken, who properly shouldn't give a toss about the Horde beyond what it can do for their Lordaeron) . Meanwhile the Alliance, being a confederacy of interdependent dominions instead of military autocracy, had players more preoccupied with seeing X race have its story advanced. The solution they came up with was to create what functioned as a blue warchief and demonstrate in game the Alliance becoming more tightly knit. I speculate that they wanted to cohesion and front of unity to give Alliance players a Horde-like feeling of being a badass military juggernaut. The trouble is, misfits uniting into a sovereign whole is appeal of the Horde; the Alliance is about independent cultures sharing certain common values sharing resources out of trust.
The other trouble is that the Horde's appeal naturally lends itself to more engaging storytelling in a combat-oriented MMORPG with PvP in it. Meanwhile, the intrigue and nuances that make the Alliance compelling plays out better in text... i.e. books, which is what we were getting. Now in 5.3, we're helping the Darkspear tribe to lead a rebellion against Garrosh Hellscream's Horde as a prelude to the invasion of Orgrimmar in patch (5.4). Many Alliance players are grousing that we're assisting the Horde instead of pursuing our own plans. The response to this, from inventing a novel and bellicose player title for the Alliance to making Vol'jin squirm in place, is an earnest effort from the developers to make us feel included. They can't go back now and make a separate Alliance story but they can try to make us feel as important in it as they can. Ah, but that offends not to few Horde players, who hate needing the Alliance (when they don't need Thrall) to keep them from imploding.
The very fact that we're petitioning for the factions to do their own thing is a big reason why the story is so unsatisfying. The developers aren't writing a story for the Horde and a story for the Alliance. Many of us think they're writing the Horde story and tacking the Alliance on, but I don't believe that's how they see it. Instead, I think that the writers see themselves as simply writing the story of WoW. They're not making two different stories for the factions because they're making one for everybody, so they think. This combined with an apparent lack of gelling with the themes and appeal of the Alliance with the game being designed is disappointing people. As long as there are two competing factions in this game and neither can win decisively for gameplay reasons, one size won't fit all.