The new combat system allows for multiple attacks on multiple targets at the same time, so there's an actual reason to carry more than one weapon at a time. But before I go full Musashi with a pair of scimitars, I must ask, 'is this viable?'
Let's look at it from a practical standpoint, using an adventurer that wields two weapons without using tricks to get a shield in as well. As an example, let's use a dwarf wielding a steel battle axe and steel war hammer, and let's call him Urist McMountainking.
So Urist Mcmountainking starts out with an axe in one hand and a hammer in the other. What's the difference between him and any other adventurer who starts out with a shield instead of a second weapon? For one, he has nothing to block incoming attacks with. He may still be able to parry attacks, but projectiles and dragonfire will ruin his day. Unless he gets good at dodging or finds effective armor, Urist McMountainking is going to accumulate injuries much faster than a dwarf using the traditional sword and board.
However, he has that second weapon to attack with. Urist McMountainking can strike two separate targets at the same time, or a single opponent with two weapons, in a single turn. He can potentially dish out more damage in a shorter amount of time than someone with just one weapon could, inflicting wounds more frequently and in general just killing faster.
In summary, dual wielding reduces the fighter's defensive ability and results in a greater chance and frequency of injury, but also increases the frequency and number of times and targets upon which a fighter can attack. In layman's terms, you take more damage and give out more.
So, what I'm asking is, it that worth it?