It's an interesting SEO case. Do you know what is my suggestion? In order to be sure is it really harder than the others, you may check how is your ranking in other search engines SERPs: check it in Yahoo.com, Bing.com, Yandex.ru (Yandex.com), Baidu.com... and then you may make some conclusions is it only a matter of the Google's algorithms or it's really objectively harder (and slower).
I'll be glad, if you share your results here later. I'll be glad too to read more about it (opinions) of other SEO members over here in this omnilogy SEO and non-SEO international forum. :)