6730 peak
1/4 of these guys are roughly playing the gamemode you are playing right now, something around 1700 players. Most of them are playing with random teammates, but let's say it's 50%. So good luck with matchmaking with only 850 players searching.
Blalord is right, the playerbase is simply too small and too divided by diffrent gamemodes. It would work if all of the players played a single mode. Note that probably a good bunch of people are playing the AI/Campaign aswell and that some gamemodes like 4v4 have a higher percentage of players compared to the rest, so there are most likely even less people in the queue.
Correct me if I'm wrong.
75% of the people playing the game mode are probably already in a match, so those actually in the queue would be even more small.