Do you actually think the odds for selecting 1 of the 5 cards is 20%? Haha, no. If you turn over a purple and 4 whites you can be damn sure you have nowhere near 20% odds of choosing that purple, and if you spend gems for a second pick you have nowhere near 40% chance, and if you spend gems again for a third pick you have nowhere near 60% chance.
You have whatever odds the devs decide that you have. The "pick one card out of 5" graphic is simply an illustration (illusion really) and has nothing to do whatsoever with your odds of choosing the card you want. If it was truly one out of five everyone would already have every purple/gold hero they have unlocked.



