I have a rapidly growing imaginary list of stupid expectations I had for Cataclysm. One was that we wouldn't be quickly outgearing heroics to the point of forgetting about CC, ever. I thought it would at least take another raid tier, or at least current players being fully geared up in the current. Boy was I wrong.
I was wrong in two parts. First off, I thought that there was any sustained desire on Blizzard's part to make heroics more challenging. Why I would think this I cannot fathom. It goes against the entire trend of what has made WoW so successful. Second, I failed to account for the fact that the current mob abilities don't require CC, our relative power levels do.
If those don't seem any different, try this hypothetical: Raging Boars hit for 500 and the entry level tank has 1000 effective health*. In other words, he can potentially die instantly, given two hits at once or very closely spaced. This is a bad scenario. It is literally a roll of the dice whether the tank lives or not. This can be easily fixed by CCing one of the boars or putting it on another tank. Or, a small health gain will allow him to survive simultaneous hits. In this scenario the power level called for CC or gear.
* Effective Health is essentially health multiplied by mitigation, but excluding avoidance. It is an expression of how much damage you can take before dying. It was the theoretical backing for stam-stacking, while the practical reason was that stamina is an easy way for simple-minded people to pick between tanks.
In the other scenario, there is one Raging Boar and one Boar Trainer. Boar Trainers have Death Aura which causes Raging Boars to hit for 100% of enemy health, one-shotting them. Gear cannot fix this. Instead the only way for the tank to survive is to separate the boar and the trainer. The boar could be CCed and the trainer killed first, the trainer kited out of range of the boar, or possibly the disc priest likes a challenge and uses frequent bubbling to keep the total damage he can take slightly above his health. In all of these scenarios it is player action, not player gear, which make the difference.
Somewhere in the middle, which is more desirable, since for many players the true benefit of gear is the ability to play mindlessly, is the third scenario, in which the challenge can be overgeared, but only at an extreme degree. In this scenario, the trainer's Death Aura only causes a 200% damage increase (1500 damage, exceeding even the 1000 damage of two boars at once), so that the required effective health is doubled when he is near the boars. This means that for most gear levels it will be necessary to use some form of CC, but eventually it may be possible to simple take the full damage and DPS quickly to avoid draining healer mana.
Raging Boars and Boar Trainers would make for a pretty boring instance, even for trash. So here are a few other mechanics which will make CC more desirable, hard to outgear, but not a permanent factor.
Fear: It makes us run into adds that we weren't quite expecting. Can be very bad on healers.
Mana Burn: Can really wreck a healer, both in dealing damage to them, but more importantly, in making a big mana pool and regen that much more important.
Roots and Ranged: This can cause a group to scatter, making control more difficulty, making AoE less effective, and possibly running into adds.
AoE spell reflection: If this mob is not dealt with quickly, casters, including paladins and DKs, are not going to be doing very well. Very quick focus fire with non-casters can also deal with this. The reflect would have to exclude spells or else rogues and hunters could become mandatory, and clearly that's a worst case scenario.
What's Aggro?: This is the simple one: a mob that hits hard and ignores normal aggro tables, encouraging CC, kiting, and focus fire.
To me, abilities with a cast time are desirable because they can allow for a more active, aware response of interrupts and target switching than a fire-and-forget CC. While I like kiting, it requires an instance with plenty of room to move, assuming our goal isn't to kill hunters. I admit, that might be a design goal for some players and developers.
I know that I've been making quite a few negative posts recently. These are not a build-up to some massive rage-quit post. My goal isn't to say that WoW sucks, which it doesn't. Instead my goal is to find ways that WoW can improve, which of course means become more fun for me, without alienating the currently gigantic player base. I have nothing but disdain for the angry posts which boil down to more or less: "WoW sucks and you are all stupid for playing it and someone should make my game with permanent death, xp loss, item loss, nine thousand person raids, and no elves or ponies." Those points accomplish nothing. They give developers nothing useful to go off of. For example, "dumbing down" isn't single, reversible change, nor is it even always bad. Frankly I am very glad that Ulduman has been 'dumbed down' with the addition of a map.