I don't know what the capacities of the phpBB web board software are.
If it is possible to alter the content retrieved by clicking the "view new posts" link it would be nice to remove posts from special subforums from appearing in the results.
Some of the special subforums have extra posting guidelines, that might not be obvious to people who read DW via the "view new posts" link and it isn't fun to type up a post only to have it removed. Not everyone is going to stop examine which of the subforums it belongs to and which special rules need to be applied. It would be more smooth just not to have posts from those boards come up in the results.
It seems to me that the idea behind having subforums is to allow people to view particular kinds of content while not having to see other kinds of content. The "view new posts" link undoes that benefit by mixing all things together.