During their first Campfire Chat livestream, Blizzard has announced changes coming to Nightmare Dungeons in Diablo 4 before the launch of Season 1 to make them more attractive than regular dungeons for endgame.
Campfire Chat Summary Nightmare Dungeons and Sigils Here are all the changes coming to Nightmare Dungeons before the launch of Diablo 4's Season 1:
Nightmare Dungeons will reward more experience to make them superior to the regular dungeon farm. Nightmare Dungeon Sigils will teleport players to the chosen Nightmare Dungeon on use. Nightmare Dungeon Sigils can be used immediately after completing the current Nightmare Dungeon, teleporting players to the next Nightmare Dungeon. . Read more on wowhead.com