Actually, its way more than a few dozen. Check out all the servers using stats and scope their stat pages. Hundreds of people play per week spread out, and i mean unique players, not compounding the dozens that play every day to get the estimate.
The problem is with a long wait before new release, Its natural to see drop off. Yes, there is not hundreds of thousand-to-millions at the same time constantly like in TF2/CSS/COD4-5 and other commercial games, but come on, they are commercial games mostly played by drone gamers who dont know what a mod is.