Example with numbers:
In a universe with 1 billion people, one person will need to have a power level 1 billion higher than normal just to raise the average by 1.
This is assuming power level = Moral level. I don't see it that way, or else it'd just be called Power Level. Mortal Level sounds more like either:
1) how advanced a biological being you are, or
2) how advanced a civilisation you are (more likely), or
3) both 1 and 2.
(2) should definitely be a part of it, otherwise a God's guidance would mean shit all. (1) would just come about from genetic engineering or from survival of the fittest.