Suggestions

This mod accomplishes the task of increasing the strength of mobs better than any other.
However I think that to reward the player for surviving much stronger enemies than normal, he should be given a higher reward than the one given in the vanilla game.

Solution

This can be achieved if when killing mobs, they drop more loot and/or more experience points according to the current difficulty value.

With a formula that could be, for example, like this:
ExperienceDropped = OriginalExperienceDropped + OriginalExperienceDropped * (DifficultyValue / X)
X Default value = 100 (changeable in the config by the player)