The play costs of the Cultist are the only thing that won't change.
But like I said in the OP, the ability cost will decrease. But right now, I'm not sure if I should increase the damage done or if I only should increase the stats.
My idea is that increase the ability damage to 7 and that I increase the attack by 2.
edit: I changed the card:
* decreasing the ability cost by 1
* increasing the attack of the Cultist by 1, by 2 for the Priest
* increased the damage of the ability from 5 to 7