Your biggest fears for 4.0

[Duelle]

I wonder if it's unreasonable to expect that SE would take the same thorough look at their dungeons as, say, WoW has when creating and adjusting the dungeon timers for their mythic+ runs, varying from dungeon to dungeon... or similarly, in applying differing rewards for each dungeon to match the time and effort necessary to complete it.

That would require them first creating dungeon tiers like WoW's normal vs heroic vs mythic, which I find unlikely given how they implement hard mode dungeons.

It would require a change in the reward structure as well, with tomestone gear being the first casualty by either notably nerfing it (to the level of the class order hall sets relative to raid gear) or outright removing it from the game.

That just might be something they're not interested in doing. I imagine a lot could be done through minimum or "dungeon" ilvl scaling, to keep the expected times and rewards around the same band, rather than needing readjustment over time as larger pulls become safer, where the rewards rather than the completion time scales with your (excess / amount reduced in sync) ilvl, or some similarly universal adjustment to mitigate need for manual/individual effort-to-reward balancing, but beyond that... I'm not sure SE will even make the attempt, or even if it'd really be worth it for them to do so?

The problem with ilevel scaling or capping ilevel is that you defeat the purpose of getting gear, which is to get stronger. I guess the third option would be weakening the gains in power from ilevel jumps (so ilvl270 gear is not notably weaker than ilvl280 gear), but I'm sure that'd lead to people complaining about how their gear is not making them notably more powerful when they upgrade one piece.

While I'd love a true exploratory dungeon, let's face it, "dungeon" itself has a new connotation compared to D&D days -- which even then may have been mixed between 'exploratory' and 'survival grinding'.

I guess I look at it differently. What I was thinking is that you're in a jungle or something with three bosses, a big tiger, a big gorilla and a giant worm. To get access to the last boss of the instance you have to kill those three bosses, but the ordered is not decided for you and instead they can be tackled in any order you want. If you want an idea of what the instance would look like, I'd point to The Black Morass from TBC; just bigger and without the portals and time-traveling dragons.

My biggest fears are the changes to the battle system. I fear they will change it too much and make FFXIV another generic action-MMO.

You might want to be specific, since the word generic seems to mean nothing these days aside from "something I don't like that I'm trying to make look bad".

I really hope they don't continue the Heavensward gear progression trend of releasing normal mode/crafted gear that outclasses the previous savage gear.

This is sort of inevitable because of ilevel jumps. Crafted gear should be able to allow someone to leapfrog having to do older content, but materia and overmelding has sort of messed that up a bit. Granted, I don't think crafted gear should be of higher ilvl than past tier gear. The Midas Savage sets were all i240, and I think that heavy metal/star velvet stuff should have been i240 to act as a starting point for those that don't want to grind lore tomestones or raid.