You have to keep in mind that even if the logical version of the problem of evil were solid, it wouldn't be a proof for atheism. At most, it would be a proof against the traditional theistic understanding of God (as a God who is active in the world). But it left untouched a God as conceived by deists like former atheist philosopher of religion Antony Flew. In this interview, when asked about the problem of evil, the deist Flew answered: "For the deist, the existence of evil does not pose a problem because the deist God does not intervene in the affairs of the world."
So, the problem of evil falls short as a proof for atheism.