One game that did a good job at scaling difficulty in recent times was Borderlands (I know I'm opening myself up for flaming here) and I think some of it could work in TES. All quests had a suggested character level next to them when given by the NPC. You could still take a quest regardless of your level but you knew you were up against it if you choose to go on a quest that was more than say 3 levels higher than that of your character. Even better, you knew that by finishing a higher rated quest you would get better loot. This predictability was nicely balanced by the uber random loot found in crates. Bosses were always at the same level too and would become easier to kill (or get to for that matter) as you progress your character.
The enemies were always at the same level even if you entered an area for non-quest specific reasons. For instance, skags (Borderlands' version of rats) would become easier to kill as you level up. None of this wolfs turning into lions turning into bears etc stuff. I think this is an important element for an RPG - you should spend LESS time killing low level enemies as you climb the ladder.
For the record; TES is a far superior game in my opinion but I do think the Borderlands scaling model provides food for thought. I'll also be the first to admit that TES is far more open world than Borderlands which certainly presents additional challenges a casual gamer like myself can't begin to imagine.