The Exp Formula[]
I deduced this formula with blood, sweat, and tears... O.k. just a lot of sacrificed nymphs and silver. It's a simple piecewise function.
x = level-1
This shows how much experience you have if you don't have any left over exp.
Estimating Max Stats[]
First of, if you look any card's starting stats for heroic, legendary, or epic you will notice that it is a direct ratio from the base card. They are as follows:
3 stars heroic : basic = 3:1 legendary : basic = 6:1 epic : basic = 12:1 4 stars legendary : basic = 3:1 epic : basic = 6:1 5 stars epic : basic = 4:1
If you know the base max stats (which a lot of muses gave their lives for), then you can calculate a good estimate of what the others are going to be and vice-versa. The margin of error I've found to be no more than a percent. I have noticed that 3 star cards tend to be lower where 4/5 star cards tend to be higher than the actual amount, but this could be just the cards that I have looked at.