I use dagger + sword for backstabbing at the moment, but usally just use the dagger for the strike (Mehrune's Razor). When I get into a melee situation outside of stealth (well, I usually try to get away, because my character's not a fair-fight kind of gal, but sometimes there's no where to run), I use sword plus sowrd (ebony + nightingale blade).
that's the problem i hade before i started to use dual daggers, 2 swords are to slow (or even sword + dagger). With 2 daggers and perks you can get close and hit the enemy and get out of his reach before he can hit you back, always move when dual wielding daggers. And they work great out side stealth give it a try. (and it's good with the perk that makes so your armor don't encomber you so you can move faster)
When it comes to reach in power attacks it just take som practice to hit them, personally i try to hit them from behinde the enemy so they cant hit me and most turn to face you. And if you get the slow time shout and use dual wield daggers you can do some insanse dmg be4 anyone knows what happend.
But remember to put more than 1 point in the armsman perk if dual wield daggers, becaus you can use the extra dmg when fighting out side stealth since the daggers have low base dmg. And until you get dark bortherhood gloves it help in instant assassination, with them you can one hit giants in stealth
