Yes, it seems that improves your Hubpages score but I think that really not much.
The best use of questions IMHO is to improve your future Hubs by asking some information related to what you wold like to write. By writing hubs your Hubscore will go higher than just only questions and answers.
And, of course questions are also a very good way to get help from Hubpages community on topics that you want to know more about.
However I'm just a Hubpages noob.
BTW: Dofollow links are the ones which are valid for search engines.