Hello!
As it stands right now a lot of things that are essentially unrelated are placed in the same forum section. A good example of this is the fact that there is only one class forum. If I'm a mage looking for info I shouldn't have to crawl through a bunch of posts about priests. Creating a subforum for every class improves the ability to find what you want and gives a better overview, decreasing the amount of topics about the same topic, and allowing people to faster find what they are looking for.
It would also be nice to have a subform dedicated to PvE, and one to PvP for the same reasons.