It has little to do with luck. Oasis nerfed drop rate heavily after players realized jackpot is guaranteed after spending certain amount of coupons (I think it was 36k). Oasis never had issues with exploits and bugs as long as whales benefited from them (Asura BT chases are still bugged), but the moment exploit was f2p friendly it was squashed (Mission Mobilization used to be missing from event cycle for months because there was a way to glitch game into reseting missions infinitely).