Weapon stats and weapons used

I am very confused, while barb has 4 weapons, which I can slot passive stats for, such as strength, all stats, etc…

But what about other passives abilities such as Damaged to vulnerability and core damage % ? Do they only work when you are using it, rather than equipping it ?

Atleast this is what it seems to me. If anyone have a solid answer, I appreciate, thank you

All of the weapon stats on your weapons are used including passives and native weapon effect. If you have two 1 handed swords, their innate crit damage (the first one below the attack speed) is included in your overall crit damage.

I have a spear that has 55% vulnerability damage Vs my dual wield that has non vulnerability damage, and I can clearly see that I hit upto 25k with spears where as the dual wield is only 13-15k

Your weapon sets can deal different damage, but all stats contribute to your build from all equiped weapons.

The difference in damage can be from different power levels from your weapon sets.

An easy way to check is to put on multiple weapons with a stat bonus and you will see it adding to the total.

The same can be said for the other bonuses, you just have to look deeper in the UI to see it.