Okay, well that thing is unrelated to the other thing. That's actually a known issue with how dual wield attacks work in the system.
During the act of attacking, each weapon is unequipped for the attack of the other hand. That means if the only source of the dual wield trait on the actor is one of his weapons, when it is removed, he's no longer dual wielding. That causes all kinds of wonky behavior, and that's why you want the trait on either the actor, or his class, or a permanent state (from the yep passive states plugin).
Good news, I fixed the problem. The issue was from the new parameter in 2.74, equip only mode, which most people wouldn't be using. I'd messed up a check for if that parameter was enabled, which was causing the isCurrentlyDualWielding() function to return true without doing any checks to see if the actor was actually dual wielding.
The idea behind this check was that if out of battle, OR if the plugin parameter was enabled, it would only ever return the actual slotType of the actor (for which 0 is normal and 1 is dual wield type). This was to maintain compatibility with in combat plugins that also relied on knowing if the actor was dual wield type or not, like the YEP equip change in battle plugin.
But since I'd accidentally reversed this check, if the parameter was disabled, it would trigger that check, which was returning if the actor was dual wield type, and not if he was actively dual wielding, as expected. Which leads to your problem, where a two handed weapon was considered dual wielding. It likely also had the same problem with actors using a shield in their offhand, although I didn't test for that.
I have uploaded v2.75 which corrected this bug. Everything should work fine now. Thanks for the report, and sorry it took me a while to find the culprit, as I said, I didn't have my test environment running on my new windows install, so I was honestly trying to avoid doing that as much as I could by asking many questions from you about your specific use case.
~Ramza