Is dual wielding worth it? None of my friends ever try it out.

If you have the Tomb of Ice expansion it's well worth it!. There is a morining star added to the town shope deck that gives you +1 damage and +1 surge. Paired with the town deck sword it's the damage output is slightly better or equal to the axe ( unless you are rolling more than 4 or more surges). Then if in the future you find a good one handed melee weapon the morning star is even better.

Other than that I think that dual wielding is a matter of preference but I always went for the axe or the sword and sheild before the morning star came around.

As a rule, dual-wielding is less powerful than using a two-handed weapon. However, a big part of the strategy of Descent is making good use of whatever treasures you happen to draw. If you happen to draw a one-handed melee weapon, dual-wielding may be the best option available to you (depending on what other equipment you have, and whether your hero is being targeted often enough to make a shield better). Starting the game with a sword + dagger means you generally do less damage than with an axe, but it gives you more flexibility; if you draw a shield, you can immediately equip it, and if you draw a one-handed weapon, you already have an off-hand weapon to match with it.

Now, there's also the issue that a shield is often preferable to an off-hand weapon, mostly because lots of monsters in Descent will die from one hit anyway, but that's not really a problem with dual-wielding, per se, it's the general problem of offensive bonuses having inconsistent value.

EDIT: The main issue with the morningstar is that you start the game with one less potion due to the increased cost.

I would have to agree with Antistone here. I believe it is more situational equipment placement in a sense. Take advantage of what you have at the time to get the most out of it.

Dual Wielding would be a better choice if there was some kind of defensive benefit, but without it, the 1-2 damage/surges you get is usually not worth it.

It occurs to me (with some amount of fear in my wallet) that Descent is approaching the point of needing a second edition.....

Later in the game when surges gain strength an off hand weapon that adds 1 or 2 could be a huge boost. Early in the game 1 surge is 1/2 a damage on most 1 handed weapons. Late in the game when 1 surge buys pierce 2 or more it could be more worth it, especially since armor will be better by that point. Also, by that point the offhand weapon will be giving a bigger bonus than just 1 free damage or surge.

The other benefit of the off hand weapon would be versatility. If you had 2 drastically different types of 1 handed weapons you could swap from high damage weapon to effect dealing weapon or pierce weapon.

The biggest boost dual wielding could get would be a subtlety skill that did something along the lines of "Count the bonus from an offhand weapon twice"

First of all, you should probably not assume that just because you're wielding a gold weapon means that you also have another gold, one-handed melee weapon granting you an off-hand bonus. Your odds of drawing two such weapons are extremely slim, and even if you do, you have to ask whether that improved off-hand bonus is really worth the 350 coins you could get by selling your off-hand weapon and replacing it with a shop dagger. Additionally, if you're using an extremely powerful weapon, most monsters you attack will probably die in one hit (at least in vanilla Descent), so getting an extra couple damage may not matter at all.

The versatility of equipping two one-hand weapons that are good for different situations is also nice on paper, but probably not so hot in actual play. How many one-handed melee weapons can you name that actually have interesting special effects? There are some that inflict Bleed, but that's essentially just extra damage--the extra randomness and the delay in its effect could make it situationally slightly better or worse than other weapons, but that's a very small difference, and the way the actual weapons are designed, the daggers of any given treasure level are essentially always worse than a sword of the same level and always better than a sword of a lower treasure level. So this is really a non-issue with the existing treasures.

You can of course keep a two-hander in your backpack and switch off depending on the situation, but that no longer has anything to do with dual-wielding.

As for the skill, I'm not sure whether you're suggesting a new skill or referencing the existing "Ambidextrous" skill, which adds +1 damage to your attack when dual-wielding. In either case, it's really fairly unimpressive for a skill, and the fact that a skill that improves dual-wielding (a melee-only option) is located in the Subterfuge deck is insulting. The version of Ambidextrous I'm including in my forthcoming Descent mod lets you add the off-hand bonus of your main weapon while dual-wielding (in addition to the bonus from your secondary weapon), and it's a Combat skill.

As pointed out above... it's all in what you have, and what character you're playing. We just got the ToI expansion, and had our melee guy switch to the one that allows you to weild a 2-handed melee weapon in one hand. Main hand is the Dragonbone Hammer (I think that's it... Copper: Pierce 2, 1 surge = 1 dmg) add that to the Morning Star off-hand, and you have a potential Lt. killer there. Which happened that same game session.

But, for the most part, one-handed and shield or 2-handed weapon will always beat out dual weilding.

In RTL it can be usefull knowing if your main weapon is crushed you have anouther ready to go. This can prevent the OL from going for your weapon at all.