Dual Wielding isnt really an issue with BG3, its a system issue. Its just that most classes need their bonus actions, and that Dual Wielding takes a bonus action. As you also said, you get limited to 1d4 to 1d6 weapons without the Two Weapon fighting style and the Dual Wielding feat, which let you dual wield up to 1d8 weapons (Rapiers for Dex, several options for Str). There are classes like Barbarian that, depending on subclass, could either wield a two handed weapon and use bonus actions for other things, or dont use their bonus action and may want to wield dual 1d8 weapons. The issue really comes down to is there is just too many free bonus actions in the game that it truly shows the issue of Dual Wielding in the 5e system. Why waste a fighting style and a feat when you can take a better fighting style and an ASI/better feat at level 4. It all comes down to that action economy and what you want to spend those actions on, and sadly some options are just not worth it.
Here's what I'm not following: you're not explaining why it's not worth it. You're making an assertion, saying it's not worth it. You're saying other choices are better and claiming they're better because of action economy. But you're not explaining why.
Example:
I have a fighter with a 16 Str, 14 Dex, and 14 Con. The fighter has the two weapon fighting style so that Str damage is calculated for the off hand weapon.
I reach level four and pick up Dual Wielder, giving me the ability to use better weapons.
So here I am. In one hand I'm wielding Faithbreaker. In the other, I'm swinging Xyanyde.
Faithbreaker does 1d8 + 1(magic) + 3(str). This is 8.5 damage on average. In addition to this, I can add in damage from the weapon's ability: Absolute Power, which allows another d6 of force damage and potentially pushes the target back a considerable distance. Or maybe I just want to make the strike a menacing attack, adding a d8 of damage and potentially frightening the target. Most importantly though, if the swing misses, there's still a chance to do noteworthy damage.
Then I've got my other hand. Xyanyde only does a d6, although it does add in my Str. This is 6.5 damage on average. But more than that, the weapon has a very good chance of outlining the target in Faerie Fire, giving me advantage on all my attacks. Meaning I'm far less likely to miss on subsequent attacks.
Adding the two attacks together, I have an average of 15 points of damage, assuming no action surge, no battle technique, and no Absolute Power, all of which would only up my average damage.
I also have action surge, meaning I'm not limited to one primary attack when it matters.
Now, let's consider another fighter so things are basically similar. This fighter uses a two handed weapon, and maybe took a plus two to Str at level four instead of dual wielder. That's an 18 Str.
At this point, plenty of two handed fighters are still using the Everburn Blade.
So. That's 2d6 + 1d4 + 4. That's 13.5 damage on average. But it's not really because this fighter gets to reroll initial ones and twos on damage. If we assume no ones and twos are rolled (although they can be on the second roll, but we're being favorable and quick here), then the average damage comes out to 16.5. If the swing misses, all the potential damage is zero.
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Assuming all hits land, that's an average damage of:
Dual: 15 (but higher if Absolute Power is used, not to mention the battlefield advantage of repositioning the target via push)
Two handed: 16.5 (technically a bit lower)
But... if I miss with a two handed attack, that's it. Zero damage. Try again later.
Whereas I have to miss twice with my dual wielder, making it the more conservative choice which is more likely to do *some* damage. And some is better than none.
And now consider, I'm *way* less likely to miss. Because my second weapon has a special ability. It outlines targets in Faerie Fire giving me advantage on all of my attacks. That's huge.
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My point here is that most of the game is going to happen after level four. Which means the dual wielder is going to be able to take advantage of a lot of combinations when it comes to the special abilities of weapons.
I would argue that some of those combinations are already powerful at this stage of the game. The most powerful of which is the Xyanyde example above, in my opinion. But there are also combinations involving the Shattered Flail.
Mixing and matching the weapon choices is not only fun, it's potential for power in combat is undeniable.
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And what bonus action am I going to trade this for?
The chance to shove? My primary weapon already does that if I want it to. Or I could use a push martial ability while adding a d8 to my attack. So, no, shove isn't attractive enough to replace my offhand attack.
In other words, where's the action economy?
Are there times where I'm going to need to drink a potion instead of using an off hand attack? Sure, probably, though I would argue that those times would be rare. Especially if I have a cleric in the party for healing and buffing or if I'm wielding a weapon that actually heals or buffs me in addition to hurting the enemy.
