Of course they ruined this in DA2 with the ability to just kite.
In SR, id like the very hard to be just that, very hard, and most importantly make you think, strategize and use all your abilities. Im not too worried about it though, they are always going to be good mods to fix these. Id like to see more than just enemy health get a upgrade on higher difficulties.
Personally, for all its faults, I found the combat in DA2 to be a lot more challenging on Nightmare (kiting and enemies dropping out of the sky, notwithstanding) compared to DA:O.
The reason is because in DA:O, "Nightmare mode" was a joke because you could simply spam incredibly cheap healing potions to get through anything. I found in DA2 I had to plan every battle a lot more strategically. I really struggled to get through almost every battle on Nightmare.
Some things I think were very interesting - gradually increasing enemy immunities (Nightmare almost every enemy is immune to something), enemy A.I. for the rogues was really tough to beat. they stealth, steal your potions and backstab you.
Obviously, as mentioned, there were a lot of other problems with DA2.
However, in Skyrim, what if certain enemies could stealth and backstab the player? In Oblivion I only remember a couple of enemies using chameleon, and they were pretty hard to beat. However they could be detected visually by a shimmering effect. If enemies can't detect an invisible player, why should we be able to see this shimmering effect?
If the player can stealth and backstab, shouldn't there be enemies that can do the same? If an NPC is sneaking and the PC doesn't notice them, shouldn't they appear invisible to the player?
And if we can use the Slow Time shout, Bullet Time Bow perk, etc, doesn't it seem that there should be enemies that can use these abilities as well?
Also, some enemies could be made a lot tougher if they use healing potions and healing spells frequently. I encountered this a lot after installing FCOM, made the game a hell of a lot harder.