One of the nerfs, the change to Improved Berserker Stance, would in fact be a buff if not for how Blizzard itemizes four stat gear vs. five stat gear. By making this change (obstensibly to point warriors at strength gear over agility/AP gear) you get a situation where fury warriors can choose strength gear with four stats to gain the benefit of their Improved Berserker Stance talent, or they can lose AP to take gear that is otherwise better itemized.
In that comparison, the agility/AP neck will end up giving you nearly 2% crit (62.5 agi = 1% crit and it's 46 Crit Strike Rating for 1% crit at level 80) and you'll trade off the lower attack power (even without Imp Zerk) for 46 armor pen. You'll lose hit rating, which is a concern if you're riding the edge of the special's cap, but in my experience most DPS warriors have loads of hit on their gear already. In other words, Imp Zerk is mechanically a buff in that we get 20% more strength and thus more AP from strength items (which tend to have more AP than agility/AP items since those items are designed for classes who get AP from agility as well, which warriors do not) but the items in the game that have strength on them tend to suffer in comparison to agility/AP items even given this mechanic because of diminishing returns on stats and the spread of stats on agility/AP gear. The higher a stat goes, the more it costs. A four stat item only has four stats to spend its item budget on, and as a result tends to provide a lower total amount of stats (and many of those points are spent on higher stamina than agility/AP gear) than the five stat pieces do, which have more stats to spend their item budget on and as a result don't have to pay for their higher stats.
Thus we have an ability that is good on the face of it but is hampered by poor itemization. (It would be far worse if Ulduar gear hadn't gone through a balancing pass that lowered the stamina for strength on DPS plate, which when it was first announced often rivaled tanking plate for stamina.) As important as this change was, however, it would have had a minor effect at best if not for the removal of Weapon Mastery from fury, the damage penalty to Titan's Grip, and the impression created by the design of fights in Naxxramas.
Frankly, fights like Patchwerk, Thaddius and Loatheb created the idea that warrior DPS was ridiculously high. A good performance by a warrior on those fights could see 7.5 to 8k DPS (especially on Thaddius or Loatheb, with their damage inflation abilities that stack particularly well with the warrior rage mechanic - the more white damage the warrior does thanks to Thaddius' changes stacking or Loatheb's crit bonus from spores, the more rage he or she has to do more damage with their boosted specials) which would effectively pad the meters for the rest of the night. A warrior who was providing a solid but unremarkable 4k DPS before those fights could easily seem to be at 5.5 or even 6k for the night if they performed well there. Warrior DPS also tended to be inflated by trash pulls, which Ulduar has less of (and those pulls tend to require more CC, keeping Bladestorm and Whirlwind from being as widely applied) which also hurts warrior DPS overall.
So there was a consensus (which the developers seem to share, which baffles me) that warrior DPS was ridiculously high. I'm aware this was also at least in part due to warriors going out and finding the best itemization for them to provide higher DPS than was expected: fury warriors with two Betrayers and loads of BiS leather gear were putting out DPS that no, wouldn't have been possible if they'd been wearing the plate gear that simply did not have the stats. It seems paradoxical to me to design a class around the idea that they wouldn't go out and get the gear that would allow them to do the best they could at their chosen role. I've seen no talent changes that would penalize a moonkin for wearing cloth, for instance.
The cascading series of changes continued with the loss of Weapon Mastery to arms. Weapon Mastery was a talent that provided some much needed 'expertise relief' to fury warriors. A raiding fury warrior with that talent in his tree did not have to spec into it if his expertise was high enough (perhaps he was main handing a Jawbone for example) but if he got lucky and a BoH dropped, he could always make up the loss of expertise by respeccing, he didn't have to gem and watchdog his gear for expertise cap at all costs. Again, by itself, this change is minor, but when it forces you to gem away from strength or ArP or keeps you from using a piece of gear which would be superior save for its lack of expertise (which you can't make up, and which arms warriors can make up in two ways) you start to see why arms has become the generally superior DPS tree for warriors. It's easier to gear for. An arms warrior with 263 hit rating has reached 8% miss reduction which will effectively cap his white attacks as well as specials, while a fury warrior with that hit rating will merely have capped specials, as the dual wield penalty will push his miss rating with white attacks far higher. Meanwhile, Arms has Strength of Arms and Weapon Mastery to both increase expertise and reduce the chance that he or she will be dodged, while fury has no talents at all that compensate for lower expertise.
The expertise loss combined with the rigid focus on strength over AP would have been enough to knock fury down a peg, but not enough to really lower its DPS compared to other melee hybrids if not for the final big change to fury, the Titan's Grip nerf. Let's just come right out and say it: 10% physical damage reduction is far and away too much of a penalty. Combined with the damage of your offhand already being reduced by half, it ends up not only reducing all damage you do by 10% (which, if you where doing 4.5k DPS before, would be a 450 DPS decrease) but it also reduces the amount of rage you have coming in, and then costs you 10% damage on every special attack you do while still charging you the same amount of rage as before for those special attacks. The new, 10% less effective Bloodthirsts you do still cost 30 rage, Whirlwind, Bloodsurge Slams, Heroic Strikes all cost the same amount of rage for their new, lowered effect at a time when you have less rage from your lower damage white attacks, at a time when you have to stack expertise to 26 no matter what, at a time when you probably have less AP than you did to further lower your white damage.
All of this combines with the change made before patch 3.1 that removed talents like Two-Handed Weapon Specialization and various Enrages from the damage calculations of Deep Wounds. Quite frankly, the nerf to DW and the changes to our itemization in Ulduar were probably all the nerf warriors needed, and it was a nerf that effected both arms and fury equally.
It's hard to make a case for arms having been nerfed in 3.1, even if their DPS still isn't equal to other melee hybrids. Arms is a much stronger spec now and is clearly stronger than fury on fights where there is mobility required thanks to Juggernaut allowing them to catch up to the boss and increase their critical strike chance when they arrive - the recent nerf to Juggernaut scheduled for 3.1.2 will be crippling in PvP, but I don't know how bad it will be for PvE, since it's less the 100% crit on a MS or Slam and more the ability to stay in close and generate rage, instead of spending it on an intercept, that makes this so good for PvE. Still, Arms doesn't perform as well as other melee hybrirds, even if it does outperform fury unless there's a lot of things around to hit with whirlwind/cleave.
Fury DPS warriors were effectively hit several times in places that didn't really require so massive a correction, and the ultimate result was the near total dismantling of a DPS spec. While it is still possible to put up good numbers as a fury warrior, it not only requires talent and a knowledge of your class but also a very particular kind of fight (one where you can remain stationary and hit multiple mobs at once) which is rare at best in the new content. XT - 002, Auriaya and especially Thorim Phase 1, with Yogg-Saron phase 2 all have some aspects of this, but all also have movement enough to keep the DPS warrior at a disadvantage and give other classes the time to shine: there are no Thaddius or Loatheb fights in Ulduar.
This one forum posting promising small buffs (and which clearly states that warriors won't see a large increase) is encouraging only in that it finally, begrudgingly admits that warrior DPS is low in Ulduar. Since the other three tanking classes are all strong melee DPS now, it would be nice for warriors to join them.