That sounds like a pretty good idea of what the problem is, yeah.
Are you also using the menu extension plugin? The equip scene will show the calculated atk values for each hand if you are, which would help show off the problem without actually having to hit something to test.
I'll look into the compatibility with the baseparam plugin, I expect it's a simple fix, I just need to add a check to see if the plugin is installed and then look at that atk value instead of the default actor one.