You only have a 20 percent chance to play the game type you need for challenges when you need stronghold or oddball. Now if you need to win one of those matches and not just play them you could be playing for quite a long time. Since people are searching for the game type they need, your whole team may leave when they find out what game type your playing. Some way to play a certain game type would be nice. If I need team slayer wins, or tactical slayer wins, no problem. The low chance just gives me incentive to leave the game and find the match I need.