I can absolutely get behind the hybrid approach, one of the critical weaknesses of “classic” forum directories which only show categories (and counts) is that they give you zero information about the most important element of any community – what the $@&# are people actually talking about here?
Another advantage of disconnecting the category list from topic display ala the Battle.net hybrid is we can show a linear list of “these are the x most recent / most popular topics” which is far better than “pick 3 from this category nobody ever goes to, pick 3 from this category nobody ever goes to, pick 3 from…” you get the idea 