Agreed, but the added reward should be done differently: add bonus rewards. Bonus rewards are calculable based on you and your team's performance (e.g. how fast you killed enemy waves, timings, etc.), whether your team won or lost, and the game length. Faster games that end within 5-20 minutes give more rewards. Bonuses are given to both losing and winning teams.
Default reward (same as usual): 125XP, 20 points. X% chance for cubelet (let's say X is 20% as an example).
Bonus: Up to 75XP and 12 points. If you win, then add (X/2)% chance of cubelet (so, if X is 20% in the example, then the bonus adds +10% chance, giving a total of 30% chance to get a cubelet).
If you lose, you get up to 50% of the maximum bonus reward (so up to 6 points and 35XP).