What if we get the option to choose the gameplay mode we want? Now, I am assuming this will be implemented at some point, but not yet as you want sufficient testing of each map and mode.
To combat this uneven testing, how about a modifier that will give you up to +25% rewards for picking a game mode that is currently not being played?
To provide an example:
If there are 100 matches in progress, and half of these are domination, then you won’t get any bonus for choosing to play a domination mode map. However, since no one is playing a detonation game, you will get +25% rewards for choosing this mode.
If each mode is equally represented, then you get no bonus. If one mode is significantly under-represented, you get a 25% bonus. If one mode is somewhat under-represented, you get a bonus depending on how under-represented that mode is. The minimum bonus is 10% (so that it actually matters; no one will care about a 2% bonus). This way, you are sure to even out the modes played.