Without any proof, I'm going to say the online player count isn't accurate as one would believe it. That's just how many people have the game up with an active internet connection. If you want to get a total idea of who is playing the game, open up the chat window and it will tell you next to "Steel Division Chat". The number is about half the actual online count at all times, because I think it counts people doing skirmish or campaign. So, at best you take half the player population and remove them from the total, and you have the online player count that's either playing games or looking for games. When you factor it like that, the total population late night PST is about 110 people or so, a 10v10 takes up about 1/5th of the population. Pretty sure that's a popular game mode, considering the other options are 1v1,2v2,3v3,4v4 - looks evenly split on the surface. I'm sure the total numbers of people playing the different small games would skew to more 2v2s/3v3s over 1v1s/4v4s but that's my guess. Overall, about 20% to 40% of the population at any time is playing 10v10s or interested in them.
Indeed cause i would be surprised there is always 200 people with the majority of them waiting in chat without playing or joining lobbys. I tend to forget my game is open sometimes but i'm not a good example