Honestly to justify any of the card drops rate I feel the first thing they should do is allow both a 4 star and a 5 star in a deck along with your other 3's. Nothing feels more soul crushing then grinding out for a 4 star card you will never end up using at all because it will be immediately outclassed by a better 5 star.

It would at least not only customize your gameplan but would give more incentive into getting those cards.