Block chance should be above dual wield in the load order, it should also be loaded immediately after YEP_BattleCore, before other battle plugins. Since it's disabled, that won't matter just now, but when you do use it later, that'll be a thing.
Dual wield should be loaded with the other Yanfly battle plugins, at least after the action sequence packs. It's probably fine where it is right now, but I'd consider moving it, just in case that's what's causing this.
With it set like this, a normal dual wield actor with only a two handed weapon, and nothing in the offhand does not attack twice using the normal attack skill.
I'd also have to ask you to check a couple of other things as well.
- Is this actually the default attack skill we're talking about, or a clone/copy of the attack skill with a different skillId? Are you using the weapon unleash plugin to replace the attack skill with something else?
- Are you using an action sequence for that skill, or just the default one?
- If you are using a custom sequence for the attack skill, could you share the <target action> section of it?
Still looking into the barehanded attack thing. I don't test very often with that parameter, so it's very likely it's been broken for some time after the 2.68 update.