This is basically just a better version of the current unicorn. Sure, no regenerate, but flying by itself is one of the best abilities in the game and prevents tons of dice. There's really no reason to give it another die AND charge.
I mean, all you have to do is give this creature Fast and you can get your charge bonus every turn without worrying about being hindered. Besides, inherently rolling 6 dice is only something that the most expensive creatures in the game can do, so 13 mana is definitely too low as a cost.
A pegasus could be an interesting addition, but it would be more compelling if it wasn't just an overpowered version of Highland Unicorn. And since it's part of the Holy school, it would fit better if it had a way of protecting its allies. Maybe something like this:
Pegasus (13 mana) (level 2 holy, level 1 air)
2 armor
9 health
Quick Attack (Hooves): 3 attack dice
Flying, Aegis 1
As a quick action, you may have Pegasus give a friendly creature Aegis 1 until the end of the round. If you, Pegasus loses Aegis 1 until the end of the round.
Sort of like a helper pony. A brony, you could say..