I think I've been here long enough to be an older member (
I was around on the old style Board for about two years before this one.)
I agree that newcomers posts can get lost if one doesn't visit the Pub. There are also variations between the number of responses received over the week and how many you get over the weekend (much more).
A separate forum could allow for meeting and greeting as well as maybe including a sticky explaining the various facets of the Board here.
However, it is true, some may not make a special trip to a separate forum, especially as it has become very tempting with all these multiple forums to settle down with the beverage of one's choice for a good string discussion on the areas closest to one's heart! With limited online time as well, it is possible that many members don't go everywhere available here anyway. It may not be to do with not wanting to say 'hi!'
The Pub has functioned well so far I think, introductions in a social atmosphere. Maybe a welcoming sticky/announcement in the Pub would provide a general welcome over the threshold as a starter, containing a brief introduction to other forums and explaining also the private forums too. (Unless invisible of course, in which case, it wouldn't be necessary.)
Just some passing thoughts,