I mean, what we are kinda looking for here is aggregating the most Options into the fewest Queues. We separate Complexity (Density, Max Enemies and Frequency, how much you have to deal with) from Threat (Enemy Health, Damage, Attack Speed, how dangerous any one enemy can be). Then we make sure our difficulties roughly match the main combinations of such:
Uprising = Low Complexity, Low Threat.
Malice = Low Complexity, Moderate Threat.
Maelstrom = Moderate-High Complexity, Low Threat. (Power Fantasy, many weak enemies)
Heresy = Moderate Complexity, Moderate Threat.
Damnation = Moderate Complexity, High Threat.
Auric = High Complexity, High Threat.
Auric Maelstrom = High-Insane Complexity, High-Insane Threat. (Very Modifier Dependent)
Havoc = Insane Complexity, Insane Threat.
Which would remove two modes and 39 Havoc Levels outright. We could also remove Heresy and make Malice Moderate Complexity, Moderate Threat, establishing it as the most normal of normal modes. This would also open two slots on Mortis Trials for Auric and Havoc difficulties.
(We could probably also work to make Low/Hi Int and Shock Gauntlet more a part of the curve and not seperate modifiers, that’d open up space on the board for more modifiers.)
I would like them to then take some of the hidden havoc modifiers and downshift them to lower difficulties. At least the increases to enemy Health. Maybe some Damage, maybe some attack speed (We can negotiate on the Bulwark). But Damnation enemies would end up closer to their Havoc counterparts in terms of stats, and have the exact same health. This would make the meat grinder a good way to test Havoc Efficacy
Maelstroms can have bespoke complexity based on the challenge type (So a “Horde” focused maelstrom might have H40 levels of Horde Density but Auric levels of Specialist/Elite/Monster density, while a “Monstrosity” maelstrom would focus on throwing more monsters, etc). Also pass the retired Havoc Rotating Mods down here for people who want to practice them without the added BS of Havoc.
Then Havoc remains the “Everything all at once” difficulty, with a boost to enemy damage and attack speed but not health. Lets also ditch the health/toughness/ammo changes. Have “Low Health/Toughness” and “Ammo Scarcity” as rotating modifiers and have them show up at Malice and above from time-to-time for the sick freaks who like those.
TLDR: I think we should be able to use the meat grinder to judge how effective something is against enemies in H40. So increasing the enemy health curve, at least across Heresy and Damnation, to align Damnation with H40 would be one possible solution.