I think the sub forums tend to be quiet because the core of the group handles helping each other directly in the game via guild chat or on raidcall. There are usually people around all times of the day though typical of this family US prime time and weekends have the bigger crowds on at one time. We usually are in the 40's at least for people on during these times, but can definitely be more. I'm saying 40's as the minimum regular populations for that time frame. I've even been on in the mornings and found 20 people at times. Even before it went free to play I never had issues finding things to do or just people to chat with in general while I soloed at any time of the day.
So just because there is not a lot of chit chat on the subforums for ESO doesn't mean a thing. Actually it means we rather be playing and helping each other within the game rather than writing things here. Most things get worked out better doing it in game anyway rather than pointing someone at something to read and if that is the case there are too many to count places with useful stuff already written we can point them at if the need arises.