keep it at, you'll get one at some point, and since you only need 1 drop for a complete playset you don't have to worry, there is still a lot of time left
It should be given a Button, where you can select the card that you most want and that increase its drop chance to 50%, but for the others -50% (1%/50%=0,5%) or when you reach 3,000,000 Cumulative Points Rewards an extra card pick.
cumulative points doesn't matter though if you are not using a farm deck or sth you'll only get 2 or 3 boxes per match which will give you some coins mostly.
I actually have 6,000,000 Cumulative Points Rewards, 65 battles against Marik (60% win) with the Ojama farm Deck (7-8K) and still I need a single "Ra's Disciple". -_- Konami must add a changed or a selected drop chance. I hope (dies last) I get him today.