I don’t like the randomness of mayhem modifiers or the lazy attempt at raising the difficulty ceiling by exponentially increasing enemy HP. We now have 10 levels in Mayhem. That gives the possibility to stack modifiers as you go up tiers. You start with a specific modifier maybe something like enemy attacks have a chance to cause a knockback. Every time you move up a tier you stack a new modifier on top of the previous modifier. Mayhem 2 enemies have a chance to spawn an elemental pool on death, Mayhem 5 enemies do double damage, Mayhem 9 enemies spawn death on death, Mayhem 10 no FFYL for example. By mayhem 10 you have 10 modifiers to deal with. No modifiers that directly nerf the player. Being able to select from a pool of modifiers for each tier would be fine too.
Nothing really works in the current state of the game with the imbalanced weapons and over bloated enemy HP but this is how I would have implemented Mayhem to increase difficulty rather than just exponentially increase enemy HP with a few random modifiers.