I've been using this mod and Scaling Health (https://minecraft.curseforge.com/projects/scaling-health?gameCategorySlug=mc-mods&projectID=248027). I prefer Scaling Health for difficulty, as it gives finer control for how difficulty increases/decrease. They work okay together, but I wish Improved Mobs would integrated by taking the difficulty from Scaling Health to change mob stats.

added scalinghealth mod support. health and attack dmg wont be modified with scalinghealth installed since that mod handles it already.