I just finished my Daily Quest. During the quest, I was able to advance to the Gold League. Now I'm at Gold League, Tier 3. Luckily I was able to finish the quest while in the higher league so my Daily Rewards were greatly improved. In addition to getting two more cards for my reward, I was also pleasantly surprised when I revealed the cards.
With 66% of my rewards being Rare or Epic cards, I would say that I was pretty lucky since the odds are only about 20% to receive a Rare or better card. I'm still holding out hopes that I'll be seeing a few Legendary cards soon in my Daily Rewards, but I'll take a set of cards like this any time.