[Plugin: W3 Total Cache] "Replace site's hostname" not working for subdomains

Anyone have any insight into this?

I have resolved this issue. I modified the w3_get_home_url() function in inc/define.php in the w3-total-cache plugins folder. You can see below that I added a line to set the home_url variable equal to the get_home_url() WordPress function (line 3), essentially treating my setup as if it’s a multisite setup. These instructions should be sufficient should anyone else experience this issue with this unique setup.

function w3_get_home_url() {
    static $home_url = null;
    $home_url = get_home_url();

    if ($home_url === null) {
        $config = w3_instance('W3_Config');
        if (w3_is_multisite() && $config->get_boolean('common.force_master')) {
            $home_url = get_home_url();
        } else {
            // get_option is unusable here, it can cause problem when objCache isn't yet initialized
            // Which is why we save the 'home' option in our ConfigCache
            // We don't just use $config->get_string, because we want the cache to rebuild
            // when 'wordpress.home' is not (yet) present
            $home_url = $config->get_cache_option('wordpress.home');
            $home_url = rtrim($home_url, '/');
        }
    }

    return $home_url;
}