[ For the newer players ] I'll clear this up for anyone who doesn't know already. Daily challenges stack up to a maximum of 3. Not 3 new challenges each day.

My two big problems with daily challenges thus far
1. The challenges are too easy
2. Only given one challenge per day

A fix that I think would make this system a lot better would be to give players 3 new challenges each day that are at a higher difficulty than they are currently at. [ Example: Deal 50,000 DMG with (insert champion) ] this may seem like a high demand of damage, but the challenges that are currently set are asking for 3,500 DMG. This can be done in 2-3 kills with some champions. Having three challenges each day also means that the rewards for completing them would have to decrease. I would assume 1,500 coins per challenge would be a good base point. This would change the maximum daily challenge reward from 3500 to 4500, at the cost of more advanced challenges.

Please let me know what you guys think about this idea. I would especially like to know what the devs think about this idea.