In a comment to the last post, Jeremy offers another suggestion for promoting Crowd Control:
Another alternative is to make it difficult or impossible for a single tank to hold threat on all mobs simultaneously.
Back in the good (bad?) old days of vanilla WoW, when warriors were basically the only tanks and had very few AoE threat-generating abilities, you *had* to CC because the tank simply couldn't hold all of those mobs at once.
In BC, when tankadins became viable, their AoE tanking abilities became the gold standard: groups forgot about CC, and other tanks suffered because groups expected them to just tank everything. (As a warrior tank at the end of BC, I routinely felt like I just didn't have the tools to tank effectively.) In WotLK, this imbalance was fixed by giving *every* tank reasonable AoE capabilities, which made CC irrelevant.
Thus the "quick" fix for the lack of CC is to nerf every tank's AoE threat generation abilities to the point where they can't reasonably expect to hold more than three active mobs at once.
I don't agree with this idea. The thing is that there is an alternate strategy to Crowd Control if the tank's AoE threat is poor. The DPS simply focuses on a single target, and nukes them down one by one.
Now, admittedly, many DPS seem to find the concept of "focus fire" and "assisting" to be advanced techniques, but there's nothing really preventing them from learning. Kind of honestly, they seemed to have the same problem with "not breaking sheep".
A tank just has to generate enough AoE threat to get past the healers. Strictly speaking, good AoE threat is not absolutely necessary, it's just necessary if people want to use AoE spells.
Tankadins really came into prominence in TBC because it was "easier" for a paladin to gather everything and the raid AoE things down. I remember seeing Hyjal tanked by Warriors, and they were fine, you just had to be a little more careful.
You could have such weak AoE threat that the healers would pull off a tank, and that would make Crowd Control much more useful. But it would also make running dungeons a bit more dicey. Sheep breaks, and the mob runs straight to the healer. That's pretty much a recipe for a wipe.
Tanking is already an unpopular role. Making it harder for tanks probably isn't the best of ideas.
In a way, that may have been the bargain: Crowd Control was sacrificed to make tanking easier, making more people willing to try tanking. Overall, I'd say it was probably a good bargain. I would rather have more tanks than more use of Crowd Control.