A new kind of hard mode?

This post over on Restokin brings up an interesting point, especially in the comment section. It says that hard modes are uninteresting for players because they don't actually provide any kind of challenge to the players' skill; players like Lissanna feel that they are just running the same old content, but now its arbitrarily harder. Although I have defended hard modes in the past, I agree with Lissanna that they are basically a lazy rehash of the same content that players are forced to run over and over again. (Although that's another issue, entirely.) She complains that her guild thinks there is no real reason to run hard modes other than the achievements, and thus they don't want to run them.

So what's the alternative? Currently, most hard modes (as far as I understand it) pretty much involve more damage and more sources for that damage. What I think would be a better idea is hard modes that actually changed the fight. After all, I think Blizzard implemented hard modes to allow casual players to see the content while still giving hard core players a challenge, so rather than just adding more damage to the fight, why not make it require more skill? I'll give some examples bellow to illustrate my point. Because of my limited experience with raids, these examples will be from basic Northrend 5-mans rather than raids. These are just ideas, and I'm sure Blizzard could probably come up with ones that would be even more interesting and be enjoyable to play.

Imagine Ingvar the Plunderer in Utgarde Keep as a raid boss. His smash/dark smash ability could extend to the entire arena, and thus all players would need to run behind a column to avoid it. However, on hard mode, every time he does it, he could destroy the column he is closest to. If you didn't have a column to hide behind, the dark smash would probably kill your raid. In order to prevent people from just healing through it, each smash that hits could also apply a debuff that increases the damage of the next smash by 25%, stacking until the player dies. Now imagine Prince Keleseth from the same instance as a raid boss. What if, on hard mode, before casting frost tomb, he used an spell that pushed all of the players away from him and put a snare on them, so that they would need to bunch up on each other so that they could be close to whoever got frost tombed and they could free that person. Imagine a fight like Xevozz in Violet Hold. In VH, the orbs he summons just take the shortest path to you, following you wherever you go, making this basically a kiting fight. That would be fine on normal mode, but what if, on hard mode, they took different paths and tried to flank your raid, and you needed to be careful to make sure they don't? That would make an interesting fight, me thinks.

These are just some example, and my limited raid experience makes coming up with more example difficult, but I think you get the idea. What are some similar hard-mode fight-mechanic changers that you think would be fun to play?