The problem with hit and expertise as stats in World of Warcraft is fairly simple: they do the same thing in practice, even if not in theory. The more hit you have up to the cap (i.e. the amount of hit needed to hit a skull level mob, which is effectively level 93 in Mists of Pandaria content since we're raiding at level 90) the less likely your attacks are to miss their target. This means that not only will they successfully deal their damage, but you'll properly generate the resources said attack would generate (if any), hold threat (if that's what you're doing) and so on. Similarly, the more expertise you have up to the soft cap (the amount of expertise needed to ensure that an attack from behind a skull level mob will not be dodged) the less likely that your attacks will be dodged, which means they're more likely to successfully deal their damage, generate resources, hold threat and so on.
Expertise' only real difference is that it also reduces the chance your attacks will be parried, at a much higher cost (the parry hard cap being almost twice the dodge soft cap) but, again, that just means that expertise does the same thing as hit twice. Since warriors don't need to worry about ranged attacks for the most part, we can be grateful that at least we don't really need to worry about spell hit caps and factoring both hit and expertise into spell hit chances. Since expertise caps out dodge chance and only then parry chance, it just becomes a very complicated means to determine whether or not your attacks do damage. In the end, while there's plenty of mechanical difference between hit and expertise, they do the same basic thing. The purpose to these stats is to give you something you can cap to add complexity to what would otherwise be a system where people figured out their best stat, then capped it. If crit is a warrior's best DPS stat, she'll stack crit until the cows blow up when she hits them, so by adding stats like hit and expertise you add a level where capping, reaching a certain level of X stat becomes a viable gearing strategy.
The problem is really that hit and expertise, because they do basically the same thing, don't serve us well. This especially becomes true when considering these stats alongside the other stats warriors will be using in their various specs. An arms warrior's relationship to hit and expertise is different from either fury or protection. This becomes even more complicated when considering SMF versus Titan's Grip, or hit/expertise/mastery tanks vs. mastery/dodge/parry tanks.
Warriors have always interacted with hit and expertise in a way most other classes don't, because our very resource generation is directly tied to these stats, and the changes to rage generation and our stances in Mists of Pandaria have if anything made that even more true. A protection warrior in defensive stance gets no rage for damage taken any longer - she or he must connect with Shield Slam and Revenge to generate rage. This is what has led to the division between hit/expertise prioritizing warrior tanks and ones that prioritize dodge and parry. In essence, the latter are willing to sacrifice the steady rage generation of an assured Shield Slam for the burstier rage generation of Revenge spam, because they see the benefit of taking less damage through a higher dodge and parry rate and rely on said dodges and parries to proc their Revenges, and are willing to miss a Shield Slam. Hit/expertise warrior tanks, meanwhile, are not just leaning on Shield Slam for their rage (and using more Shield Block/Shield Barrier to actively do what dodge/parry tanks are doing passively) but are counting on hitting with their Devastates in order to reset Shield Slam's cooldown, and don't want any of those reset Shield Slams to miss.
This leads us to ask if tanks want to cap hit and soft-cap expertise. Hard capping expertise to push boss dodge and parry off the table would be prohibitive for any tanking warrior. But soft capping it to remove dodges is feasible. Pushing both hit and expertise to 7.5% (the current amount needed against a level 93 for a level 90 player) is feasible, but very expensive. Prioritizing hit and expertise over dodge and parry to the level this would require is, in my opinion, not yet practical for most warrior tanks, as I believe it would require on average ilevel 489 or better in most slots. I personally have both my hit and expertise at 4.5 to 5%, because I can reach those targets and still maintain reasonable dodge and parry. It ultimately depends on how active you can be with Shield Block and Barrier, and whether you prefer relying on steady Shield Slam rage or like hammering Revenge. Revenge is much more efficient rage generation when you're tanking multiple mobs and can almost guarantee a dodge or parry will light it up, but against slow swinging bosses steady Shield Slam rage gen is often the key to using your active mitigation properly. I admit I have a couple of alternate pieces in my bags to pump up my hit/expertise for bosses like Feng and the Spirit Kings.
Meanwhile, for DPS warriors, the value of hit and expertise shifts depending on what kind of DPS warrior you are. Frankly, while I understand the ideal presented in this coffee with the devs post, I don't think it's working out that way in actual practice. As a fury warrior, hit isn't a stat you can cap feasibly. You could burn every spare piece of gear you have that doesn't have hit on it over to hit at the reforger, wear as much hit gear as possible, and gem for hit and you're not going to cap hit. And while you're busy not capping hit, you'll also be trying to get expertise to cap. That's a very large amount of itemization budget going towards stats that simply stated keep you from whiffing when you swing. The dual wield miss penalty is so extreme that it has become somewhat ridiculous.
Tanks and arms warriors have 7.5% hit to worry about, and that can be somewhat daunting at start of expansion, but we know gear will get better to the point where those caps are achievable. But hit for SMF and TG warriors will probably never reach the point where capping hit is even feasible - it didn't last expansion, and only did so the expansion before at the very end of the fear cycle. What is the point of having a DPS statistic that is intended to get you to think about the value of capping that stat, when the cost of capping it is always prohibitive? Right now, for a fury warrior, since so much of your rage is generated by Bloodthirst anyway, capping those white hits for extra rage generation is not only not feasible it's wildly pointless to even try for. You'll cap specials (the same 7.5% that actually caps out arms and protection), get your expertise dodge capped, and forget both stats forever. Crit, mastery and haste are all far more attractive than chasing the hit rainbow.
Arms warriors, meanwhile, rely heavily on Overpower, an attack that cannot be dodged. Furthermore, when someone dodges an arms warrior, Overpower lights up. So capping expertise is less attractive to arms warriors. Granted, you still don't want Mortal Strike to be dodged, since it generates rage, but the occasional dodge won't kill you, since you'll just get to hit overpower again anyway, and as such capping expertise loses its luster in comparison.
All of this points to a mechanical problem with the execution of the idea of cappable stats providing more interesting gearing decisions. In essence, they're not providing those decisions. You're not free to choose whether or not you'll cap a stat - your spec does that for you. In fact, only protection has the leeway to make actual interesting decisions about whether or not to cap hit and expertise. Arms and fury make their decisions based entirely on their spec and the feasibility, while protection can have two completely different gearing philosophies and both can work. And part of the problem is that hit and expertise simply don't do anything compellingly different from one another. In essence, it's time for one of these stats to go, or for them both to be combined. They essentially have been combined for casters, it's time to bring them together for melee as well.
At the center of the fury of battle stand the warriors: protection, arms and fury. Check out more strategies and tips especially for warriors, from hot issues for today's warriors to Cataclysm 101 for DPS warriors and our guide to reputation gear for warriors.