Don't be too hasty
Haste certainly isn't useless for death knight tanks, in theory. Not only do you get more threat, but faster rune regeneration means more Death Strikes, and more auto attacks means more Scent of Blood procs. But haste simply doesn't make up for the lost survivability you get by eschewing all that mastery and avoidance, and if you need more threat or DPS, getting hit rating and expertise to 7.5% each will get you more bang for your buck in most situations.
Oddly enough, the haste protection paladin works similar to how a death knight tank is often described to work: you take larger spikes of damage due to a lack of innate defense, but you have a large range of active defensive buttons to pick up the slack. Haste simply helps the protection paladin use those cool downs more often and to greater effect thanks to Sanctity of Battle.
So the question here is, should DPS stats be more important for all tanks, and if so, how should Blizzard implement it?
A Blizzard of new stat options
On the side of making DPS stats important is the idea that it would provide for more meaningful and interesting choices when gearing up your tank. Rather than "best in slot," you'd have at least a chance at a more meaningful choice at what gear to wear and what to gem or reforge for. In addition, with threat and DPS potential slowly slipping away from blood tanks' hands, an opportunity to get them back would certainly be welcome.
On the other side of the coin is the argument against complication. Many members of the WoW community are already pointing out how complicated boss fights have become. Adding another layer of difficulty in the form of figuring out how to juggle up to 7 secondary stats (hit, expertise, mastery, dodge, parry, haste, and critical strike chance) might be going beyond the pale. In addition, while Blizzard's pretty big on gear consolidation, a lot of DPS would probably be a little miffed that that great critical strike trinket is suddenly a perfectly reasonable thing for a tank to roll on too. More players going after the same piece of loot may make things easier on the itemization developers, but it could lead to hurt feelings and lack of variety in a raid.
One thing to weight here might be the possibility of streamlining stats anyway. In previous columns, we have discussed some of the problems with hit rating and expertise. Hitting specific numbers with hit and expertise can get frustrating, especially with the over-abundance of hit rating on weapons and trinkets in Throne of Thunder. With Blizzard designers such as Ghostcrawler acknowledging this on twitter, we could see a removal or extreme revamp of these stats in a future expansion, thus paving the way for haste and critical strike to become important for tanks without completely overwhelming them.
Can we do it?
Of course, if you decide the positives outweigh the negatives, how do you implement it? You'd need to add some extra incentive to haste and critical strike to make them worthwhile. On the haste side, you could simply buff Scent of Blood until it becomes powerful enough, or procs often enough, for haste to be worth getting for more Scent of Blood procs. Another idea might be to apply a Sanctity of Battle-like effect to all tank specs. Blizzard's often talked about preferring classes to be more "active" in their tanking, and while paladins might initially dislike sharing one of their signature passives, it could end up being a tidy, simple way to move toward the active role, and within an expansion or two, many might forget it was once paladin-only.
On the critical strike side, the most likely candidate might be a proc of some sort. Bears, of course, already get a critical strike heal from Leader of the Pack, but we'd probably need something even more beefy to justify using it. One idea might be to allow Blood Shield to activate or be added on to from a critical strike, allowing for some fun synergy between mastery and critical strike. That also solves some of the problem of the randomness of procs by tying it to the predictability of a Blood Shield, so you know exactly what you're getting and already have it tied up with Death Strikes.
Should we do it?
In the final estimation, I have to say that I'm content with mastery, parry, and dodge as the main tank stats, and I really wouldn't feel in a hurry to change that. The high complexity of the modern raid boss battle makes me hesitant to complicate gearing on top of that, and I prefer that a tank's main job remain gearing for straight, uncomplicated survivability. What problems we do have should be fixed by new or buffed skills or mechanics, not by introducing a whole new itemization scheme. Still, the idea of haste and critical strike as tank stats and as a way to fix whatever problems we may or may not have is intriguing enough to look at, and with a new expansion almost certain to be announced at BlizzCon, a little bit of speculation never hurt anybody.
Learn the ropes of endgame play with WoW Insider's DK 101 guide. Make yourself invaluable to your raid group with Mind Freeze and other interrupts, gear up with pre-heroic DPS gear or pre-heroic tank gear, and plot your path to tier 11/valor point DPS gear.