I prefer BL2’s concept around making tougher versions of base bad guys for each successive VHM that scale with level caps. For example, for Normal (NVHM) you had Psychos that scaled up to level 30, depending on where you were in the storyline. For True (TVHM) you had Armored Maniacs that scaled up to level 50 and for Ultimate (UVHM) I think you had Legendary versions that scaled to the player’s current level (in other words, no level caps).
NVHM allowed for casual players to experience the full narrative and the basic game play. TVHM provided challenges for more serious gamers and rewarded casual players looking to extend the playing experience. UVHM was designed for the more hard core types who wanted to max out their builds and try different build/loot combinations and game play mechanics. So in essence, NVHM catered more towards those who prefer a narrative, Role Play experience. TVHM struck a balance between Role Play and Game Play and UVHM was more about the mechanics of Game Play.
I think that in terms of overall progression mechanics for end game, this three tiered approach is superior. The hit point versus damage scaling problem would need to be resolved regardless of how many tiers there were, but having three creates a harmonious balance for all players. And having three provides a base level of stats for NPCs and equipment to work off of in terms of scaling - kind of like mini-quantum jumps that provide instant harder difficulty at the beginning but then gradually advance until you reach the level cap.
That said, I think Mayhem should be an overlay of whacky modifiers that sits on top of any of the (three) playing modes. I think that Mayhem should create just that… mayhem. Mayhem for players and for NPCs. Increased spawn rates, badass mini-bosses that attack everything, etc. Leverage some of the mechanics from Mad Moxxi’s Underdome Riot - Gun Wave, Horde Wave, Badass Wave, Boss Wave, etc. as well as loot/re-supply drops. Keep some of the existing mayhem characteristics. A handful of these mayhem Modifiers might actually impact damage or health, but the entire mode would not have that built in as a scaling mechanic.
By separating Mayhem modifiers from the various VHM’s, you eliminate the situation where everyone immediately maxes out Mayhem in order to obtain the best loot drops. By re-introducing three tiers of Play Modes (NVHM, TVHM, UVHM), you then provide gaming environments that all types of fans can enjoy while allowing all of them to also experience the full gamut of Mayhem within their preferred gaming styles.
The points that I am trying to make and the solutions that I am trying to put forth are vastly more intricate and complex than what I have touched upon here (and that can be boiled down into short posts), but I am hoping that most people get the gist of what I am saying. Bring back three tiers of play modes (NVHM, TVHM, UVHM) that create a balance between Role Play and Game Play to satisfy all types of players, and then provide a separate set of Mayhem Modifiers that create crazy situations that are not tied to any one mode or to enemy/equipment scaling.
Edit: Oh, and drop the Anointment buffs down to TPS levels. Remove them from the scaling equation completely. You could also create three tiers of anointments that match each play mode if needed/desired. And lastly, regarding anointments, make them trinkets or some other attachable item that can be swapped between pieces of equipment.