I don't see why someone should want to have dummy pages. I don't think it's a good idea.
To me all it does is duplicate the number of pages of the website.
Someone clicks on a link on page "C" that goes to a page "B" (dummy page) which does nothing but forwarding to page "A". Why not link from page C to page A directly?
On my websitehttp://iwebfaq.org/site/iWeb_FAQ.html
you'll find that clicking on Forum in the menu gets you to a dummy page which forwards you to the forum. In this case I think it's a good idea because the forum is not part of iWeb and that's the only way to have the Forum appearing in nav bar. However I wouldn't use this technique for an entire website (I actually would only use it for the Forum and that's it).
Maybe you could look into making a menu using an iFrame as on my website (explained in the FAQ). SO you don't have to edit the whole website each time you add a new page or something, instead you only update the page in the iFrame.