The deal with the downloads to online player ratio is due to many factors.
In my opinion the main reason, after choosing to actually play online which one cannot hope to really affect, is Server Selection.
Problem: When going to choose a server, Apoc comes up first, so that is where many people may go; I know that’s where I went. Before you get to main, you see beginner, both of which are preceeded by tons and tons of mostly unplayed servers.
Possible Solution: When a player logs onto a server, log that event, possibly by having the server send you some sort of information. You can use those logs to rank servers. Using the ranking system you can sort the servers when people refresh the list. May be a lot of work, but the players would easily see which servers are active, and I’m sure main would be somewhere at the top.