I did /bug this in game regardless, but the Igneous Weapons tooltip says it "increases the damage of your heavy attacks." However, it still retains its pre-1.6 effect and is buffing my raw weapon damage. It's more than a UI error also, as my damage with focused aim was increased ~2k from stealth with the buff active.
I'm assuming this is a bug (though I wish it weren't) and was just wondering if ZOS could clarify.