DPS Compendium - Elitist Jerks
Dual Wielding can only really work with one spec, which is the Tri-Spec (more on that below). It has the downside of having a lot more misses, but has an increased portion of white damage, making haste more valuable. It relies on hitting a lot (and fast) to generate a lot of procbased attacks. It also uses Howling Blast as it's primary source of damage, as it's independent of weapon damage.
A frequently asked question is whether or not to Duel Wield. While early speculation has shown a wide range of effects of Duel Wielding, it certainly seems like a powerful approach. As of right now, most Death Knight dps models are built around Two Handed Weapons, and I would not suggest moving from there just yet.