I'm also having problem with this new way of adding hooks. For example, when adding Homeslider to a new hook everything is working great except that no .css or .js files gets added. I can edit the .tpl files and see the changes so that works as it should, but when I look at the source code of the page I don't see the .css or .js files.
I'm using the below method of adding files which works fine using the old way of adding hooks.
$this->context->controller->addCSS($this->_path.'flexslider.css');
$this->context->controller->addJS($this->_path.'js/jquery.flexslider-min.js');
$this->context->controller->addJS($this->_path.'js/homeslider.js');
return $this->display(__FILE__, 'homeslider.tpl', $this->getCacheId());