Nah, there is a simple thing that people don't want to admit. The more people there are in the party, the less hard they have to try.
Solo content - You can't be carried through it. The game honestly needs a few more of these as level/skill gate-keepers, and I'd probably advocate for at least one to be thrown in at the level 30 job quests to monkey-wrench the bots, but anything predictable is a pushover for bots. Hence any "random" elements should be in solo content designed to test your reaction time. Like a Bardams Mettle Boss II. That boss was actually a good way to see who actually is paying attention.
Duo content - I've only seen one of these in FFXIV, the Valentione event. This was actually a quite fun thing, but it's painfully obvious that this can't be done for anything short of mazes, where one person opens the door for the other. You can't balance a combat dungeon with less than 3 players.
3-player/4-player/5-player content - The One or more DPS can be carried through it, Game balance is dependent on all DPS players at least playing equally. Third party tools suggest that the Machinist is the worst DPS and the Summoner is the best DPS. Those pet's should in theory count for half the DPS of the pet owner, but doesn't.
6-player/7-player/8-player content - Now you have enough space in the party for one tank, one healer and any number of DPS to slack off.
24-player Alliances - Take the above 8-player content and multiply it by three. So other than mechanics that specifically require addressing three separate mechanics (like the "pads" mechanics) , you can have two entire parties slack off/eat dirt/goof-off and still complete the fights.
Realistically, the hardest content in the game should be the 4-player content (if not the solo combat content,) but instead it's the 8-player Savage content. Perhaps SE should consider making savage content 4-player content, and make storyline content 8-player content.