It can be very dependent on some of the factors I listed above.
Taking the Quest Priest list, I see they can manage to have
0-3mana : 8 cards
4mana : 5 cards
more than 5mana : 17 cards
It being a control list.
now, we look at Highlander Rogue
0-3mana : 13 cards
4mana : 3 cards
more than 5mana : 14 cards
(mid-range?)
Face Hunter
0-3mana : 26 cards
4mana : 3 cards
more than 5mana : 1 cards
(aggro)
0-3mana : 18 cards
4mana : 4 cards
more than 5mana : 8 cards
(zoo)
Interestingly, we can see a small representation at 4mana range across multiple achetype. As we look back at our own list, we can better comapre and discuss the mana curve and how it affects the potency of it.