I know this is a single player game, but players shouldn't have to deliberately avoid doing powerful things in order for the game to remain interesting.
[Old person rant] Really? Those of us who played D&D back in the day before computer games were the rage had to decide whether to play a Monty hall style campaign, where you quickly Get +5 avenger swords and wipe out demi-gods with regularity, or whether it was more fun to play a toned down game where a +2 sword was a big deal. It all comes down to what you consider fun, not how you can best optimize you power. In Oblivion, I played a total Paladin character (totally loved it, btw), with 0 levels in sneak, etc. There were no restrictions stopping me from sneaking, theiving or using descruction spells - I did use those because I was role playing. Me finding out that it was possible to break the game with armor that nobody could hit didn't take away from my enjoyment at all - I just don't get the attraction.
If you're playing a thief, is it realistic that you would have two daggers AND two buffed sword or axes? Maybe you might have one sword and one dagger like Drizzt's foe, but really, would you have 4 weapons?
Again, role playing games aren't dependent on complicated skill trees or the like and prevention of exploits. If they are good, they should depend on you using your imagination. By this measure, Skyrim, and Oblivion before that excel. If it turn s out here that destruction by itself doesn't equal 3 intermixed melee skills, so what? Is it a bad thing that you need to take 20 minutes in a battle where the vid guy did it in two? Said another way, I spent 2 1/2 hours real time cleaning out a basic kept w/bandits that my son's fried (orc, heavy armor, 2 hand, crafting) did in 10 minutes. I still say I had the better playing experience.