The probability for obtaining fighters is displayed clearly. We do not weight probabilities, so streaks of being lucky won't prevent you from continuing to get amazing fighters, but streaks of being unlucky will not guarantee you getting the fighter you want. We do not influence the randomness of the draw; it is completely up to the system.
We do monitor drop rates across the entire game system to ensure the system is behaving normally. We take any deviations from what is statistically expected seriously to ensure fairness for all players.