A lot of people feel that Crowd Control should be more prominent. You should have to Polymorph more, or Banish, or even Sap. I am not entirely sure I agree with this. I'm not sure I disagree with it either. I remember the days of Sapping or Sheeping, and they were kind of cool.
However, when I think of Crowd Control, I think of those demons in Tempest Keep. The ones with the Buzzsaws of Doom. You may remember them. If you failed to CC them, they started launching buzzsaws at the raid, doing massive damage before you could get them locked down again. Even the gap between Banishes was dangerous. Kind of honestly, I would rather not see trash like that again.
The thing about Crowd Control is that, in order for it to be used, the mob must be too dangerous to leave active while other mobs are alive. That means if you make a slight mistake, it often leads to a wipe. If the mob is any less dangerous, then it will just be tanked down.
Another problem is that mob must eventually be tanked and killed. You can't really make an untankable mob and expect people to control that. So the controlled mob exists in this zone between "can be tanked" and "cannot be tanked". And the better the gear you get, the more the mobs move to the "can be tanked" category.
I suppose if you really wanted to enforce Crowd Control, you have to create dependencies between mobs in the same pack. For example, Mob A applies a debuff to the tank increasing Fire Damage taken by 500%. Mob B does Fire damage. The optimal solution here is to fight the two mobs seperately, either by using two tanks or crowd controlling one until the other is dead.
I think that would be a fine mechanic to use once or twice. But if every trash pack started having these dependencies, just to force people to use Crowd Control, it would soon seem contrived.