Where did the Nightmare and Hell difficulties go in Diablo 3 after the expansion?

Solution 1:

The old system of "Normal/Nightmare/Hell/Inferno" is gone completely, in favor what resembles the old Monster Power selector. New difficulties are called:

Normal - Hard - Expert - Master - Torment I - Torment II - ... - Torment VI.
(Torment VII through Torment X are coming in Patch 2.3)

New difficulties are defined as a direct multiplier of monster's hit points, damage, experience gain, gold rates, and drop chances. For example, Hard, compared to Normal, grants:

  • +100% monster health
  • +30% monster damage
  • +75% experience from monsters
  • +75% gold dropped.

Difficulty of any given game is determined by its level (taken from the level of hosting player) and difficulty itself, in its new sense. So, level 35 monster on Normal will be weaker than level 30 monster on Torment I.

Below is a table of different difficulty aspects I've compiled during Patch 2.0 (some things may have changed).

Table

HP - Monster hit points, Dmg - monster damage, GF - gold multiplier, XP - experience multiplier, DB - chance of Death's Breath dropping from Elites, Leg% - legendary drop chance, Rift% - legendary drop chance in Rifts.

per lvl - increase relative to previous difficulty level, dmg inc - how much damage should a player do compared to previous difficulty level, to achieve equal farming speed.

Solution 2:

To sum up the changes: The old difficulty system "master one level and advance to the next" is gone completely. You can now choose your difficulty settings from the beginning. The higher the level the more rewards you can earn, but the nastier are the enemies.