Can dual wielding be an effective strategy?

I found dual wield doable (and fun) in a few ways:

• Heavy armor paladin.
• Sneaky character with extreme illusion and the 15x sneak damage.

The paladin could heal himself and the heavy armor negated much of the damage. Next to that I developed a knack for dodging incoming blows which makes fighting one opponent extremely easy. The sneaky character pacified (charmed) the attackers, snuck behind them and stabbed them. Both characters were played on master difficulty (I like the challenge), which means you'll have to be very patient (aka dying a lot) early game anyway, but when past level 35-40 it becomes almost too easy. The sneaky character had to hit multiple times though for killing anything above bandits since master difficulty gave enemies extreme amounts of health (or just nerfed your own damage).

There are plenty more builds to think of, but since you are indeed vulnerable to incoming blows you'll need some way to negate or dodge incoming damage. Skyrim provides quite a few ways to do this (armor, spells and actually moving your character out of harms way) so even an unarmored mage could pull off dual wield in theory. (That would make for a fun character btw: unarmored priest dual wielding maces.)

There are many situations where your enemies are not that strong, and you are not that worried about dying. In those situations, you can take advantage of dual wielding's higher damage output and kill everyone quicker. With Dual Flurry perk, your weapons deal out damage 35% faster. It's a very powerful way of increasing your damage, and it's especially good if you have enchanted weapons. In late game, especially, when you have good armor rating and high health, you won't miss being able to block that much.

Dual wielding can be very powerful for assassins. If you dual wield daggers and do a dual wield attack, you can get two powerful backstabs instead of just one. With 15x perk, 2x Dark assassin gloves, it gives you as much damage as hitting your opponent 60 times with that same dagger.

You do not have to commit 100% to dual wielding. I personally find it best to switch it up between shield-and-weapon and dual wielding depending on the situation.