EXP Parties as an option please!

[kyuven]

Just make it so that ANY combination of ANY jobs can clear ANY exp dungeons.

Diablo 3 and FFXIV, nor FFXI, are even close to the same type of game.
Having to balance content for completion by any combination of classes/jobs is a development nightmare that is PROBABLY partially the reason Diablo 3 took over a decade to complete.
If you try, people will either come up with their own golden trinities and have exclusionist mentalities, or the content is so easy it can be done in your sleep. Unless you REALLY emphasize mechanics over boss stats, this is what you get.
And then people would complain that they can't do X dungeon as Y class, while at the same time complaining that Z dungeon is too easy or N dungeon is too hard.