What precisely would lead to epiphenomenalism? I think the AfR would more or less be effective (if it is sound) against all naturalist positions on the mind (assuming naturalists can't accept mental causation; and, as Reppert put it, it would be a strange kind of naturalism that could), not just epiphenomenalism*. Nor do I think epiphenomenalism would be a good response to the argument for the naturalist, because it would still sever the causes from the process of reasoning. 

*I'm assuming epiphenomenalism is a form of naturalism, but it could be considered dualism (though one that still is vulernable to the AfR).