This is about the most obviously NOT Random, and NOT Luck exercise in the entire game. I have had the following happen 5 times in two days. Refresh and get 4 blue or purple heroes, then shuffle and turn over a a card where one of them should be, If luck prevailed, I should have pretty dam good odds (80%) to get one of the blue or purple. Each time I did this, I always got the lowest possible hero in the cards, no matter what card I picked.