I do like the idea of all dungeons being variants but with one small change.

Each path has a difficulty setting.

If people want to run harder dungeon content, they can go down the hard paths, and of course, get better rewards for their time.

Path 1: Easy (current dungeon level of gameplay)
Path 2: medium (Variant Dungeon level of gameplay)
Path 3: Hard: (Slightly more boss mechanics)
Path 4: Extreme (Much harder bosses)
Path 5: Savage (Extremely hard dungeons, only people in the best gear and experienced players will be able to clear it)

Look at that, content catered to everyone!