Many of my LS's and my FC have been discussing this topic over the last few weeks so I thought I'd provide forum input on the subject. FFXVI:ARR supports structured leveling via scripted instancing, and to some degree, FATE's. These additions were a definite improvement over it's 1.0 counterpart. However, it left the more traditional players (and possibly your more hardcore levelers) without their more preferred form of partying, open world dungeon exp farming.
Here's some ideas for it's structure (since simply burning down insta-kill mobs over and over would be too similar to a fate experience):
1. These dungeons are separate from the over-world
2. Various levels exist within each dungeon to cover varying levels of players
3. Optional Level sync offered while within these dungeon (at least up to a point in which you cap out depending on the dungeon's recommended level :: just to prevent higher level trolling)
4. Monsters within these dungeons are either of equal difficulty to scripted instance monsters or possibly much harder (I prefer harder since I'm actually looking for a challenge with some degree of randomness when leveling my other classes).
5. Due to their increased difficulty and time to kill, these monsters provide much greater EXP/kill (rejoice all weak aoe/focused dps classes)
6. Monsters have a chance to drop chests which can contain gear, items, and possibly gil.
7. Boss FATE's are littered around these instances and spawn less often than Over-world FATEs (45 minutes - 2 hour respawns)
8. Boss FATE's require at least one coordinated party to take down.
9. As someone mentioned in an earlier post, a limited number of chances against these bosses per player(or party) would make the fights more interesting and require the party to coordinate, as well as increase risk and possibly excitement/sense of achievement.
10. Since boss FATE's are difficult, they provide ample rewards upon defeat such as gil, gear, items, EXP etc.
11. Boss FATE's in these area's reward EXP even if a party reaches the maximum number of wipes, based on performance of the party during the fight (which should always be good enough to be slightly better than or equal to the EXP the party could have gained if not attempting the fight).
Well, I've run out of ideas for now haha. SE said they desired the creation of an MMO which suites as many play-styles as possible; I believe this would make a wonderful addition to the game and could possibly appease the FFXI/traditional MMO fan-base as well as players who desire a bit more of a challenge while leveling new classes/jobs. I understand that Over-world FATE's and Scripted Dungeons still need some work, but this is "food for thought".
Thank you for taking the time to read my thread. /bow