Bit early maybe, but I'd like to read more opinions on other old time FFXI players concerning content difficulty in FFXI.
First of all a premise, what is "difficulty"?
I don't think there is an unambiguous way to define it, it's subject to context, personal opinions and scenarios.
Ultimately the most efficient way to measure it would be by amount of players completing a specific content in a window of time post release. A smaller number of players completing a content X weeks after release, would hint at that content being more "difficult" than others. With the uningnorable key aspect that it's hard to measure it since there is no official, open and transparent list (like in WoW for instance) and we only get approximate values from boards like FFXIAH, where only a small part of the overall player base participate in discussions, hence this can lead to biased perceptions.
Also right now we have a much smaller player base compared to several years ago, this skews the results because there are less overall attempts at a specific content, at the same time on average the player-base still playing these days is likely more proficient at the game than the average level we had several years ago.
The amount of different tools in the players' hands and how widespread they are compared to several years ago, also affects the result.
From the developers' point of view
"Balancing" the difficulty of content for Devs is much higher when you have too many variables at play.
This is exactly the reason why over the years most MMOs, following WoW's model, tried to standardize these variables.
With less and less of them at play, it's easier for Devs to "control" the environment and hence create a more predictable one where the difficulty isn't too hard or too easy according to those variables.
WoW started this progressively with several steps bit by bit. The most important one has been the "homogeneization" approach started in patch 3.0 (WotLK), followed by 4.0 (Cataclysm).
In FFXI the definition of "roles" according to the trinity system is more bland. This is made furtherly complex by the fact you can customize role/purpose by combining different subjobs, by variable number of players participating in the content (3-18) and by the fact that there's a plethora of different support buffs, most of which can be combined together because they don't share the same slot.
This makes it incredibly hard for devs to "balance" content because players have too much freedom and what can be borderline impossible with some setups, becomes a joke with some combinations (synergy) of specific jobs/buffs.
Lately SE tried its own way to "standardize" things without completely changing the game approach like WoW did.
They did this by creating limitations (6 people content, no subjob, WS wall), immunities (targets immune to several abilities/spells/effects) and "fuck you" mechanics (instant death, unresistable full dispel, AoE weakened status, targets ignoring enmity rules, systems that require a specific proc with that proc getting progressively harder to activate each following time) and much higher HP pools of targets (making zergs with buff-stacking and short duration invincibility things like Perfect Defense, uneffective, especially in environment where content is fixed for 6 people and not variable).
All of these features together greatly limitate the excessive freedom in the hands of players, making content somewhat more "equally difficult" instead than being excessively difficult with some setups, but easy with some others.
A Retrospective of end-game content difficulty
Here's my personal take on some end-game content I can think of
Abyssea
Difficulty increased with each release, but ultimately it wasn't too high thanks to the extreme power granted by zone buffs, atmas, proc system and last but not least Primeval Brew. Once you unlocked all the "good" stuff, it wasn't really a big deal. Also you had the freedom granted by being allowed to bring up to 18 people. Same old FFXI situation with some stuff being very hard with most setups, but extremely easy with multiple specific setups. Also things progressively became easier and easier as you unlocked stuff (KIs, Atmas, Buffs, last but not least increased level cap)
Voidwatch
Situation similar to Abyssea but with less "power creep" because it was already level 99 content and Atmacites/Buffs were less powerful than in Abyssea. The hardest fights in Voidwatch were tough and hardly farmable by anyone, but still doable once you unlocked the right stuff and used one of the multiple available "easy" setups.
Legion
No Atmacites, no zone buffs, the addition of (back then) new zone enmity rules, several fuck-up moves but you had the "freedom" of bringing up to 18 people. Content was very, very difficult but if amount of support jobs with necessary gear and amount of addons (react etc) were as widespread as they are today, content would've been perceived as easier. Still, much harder than the others listed so far.
Delve
Difficult content requiring the activation of specific gimmicks (granted by specific setups) on most of the NMs involved. Doing all 6 bosses in the same run was challenging at start, especially because of the lack of gear options due to the transition to ilevel paradygm. You still had the freedom granted by up to 18 people and had mostly to rely on stunning the dangerous moves. Difficult, interesting and "fair" content. Arguably full-runs granted too many points compared to the non-complete runs and with the amount of gear options we have nowadays, it would've been trivial.
Incursion
Hard because of the uncommon (back then) zone enmity rules, the amount of AoE moves and frequent dispels, in addition to very dangerous moves from some NMs. Difficulty was potentially very high at the maximum level, but you didn't really have all that need to farm the content at the max difficulty level, it was unefficient and unnecessary (as a matter of fact, only a couple of groups managed to, back then)
Vagary
Content was unfriendly for melee, which is one of the reason why mage setups were so favoured. Several fuck-up moves but there were multiple ways of dealing with them, in addition to the freedom granted by the up to 18 people. Easily farmable once the pop conditions were found out.
Aeonic (Zi'tah, Ru'aun, Reisen highest tier battles)
The hardest fights were quite challenging, notably WoC, Kiryu and the 7 Reisen bosses. That's before the SMN burns became widespread. Ultimately power creep (from Job Points first, then gear) made the content progressively easier but at start it was quite tough. Despite being able to bring up to 18 people the HP scaling of bosses arguably made killing with 6-8 people easier than bringing 18
Omen
Content was tough when you could only bring 6 people. Being able to bring 18, the tweaks to some moves of the minibosses and ultimately the power creep from gear/job points made the content quite easy and accessible
Master Trials
These were quite tough, especially but not only for the 6 people limitation. The entry cost and cosmetic-only rewards didn't make it that popular for a lot of players, at the same time though you didn't feel like you were missing out a lot by deciding to skip it (sigh). Ultimately made easier thanks to the power creep (Job Points, Gear)
Divergence Dynamis
The biggest enemy in here was lag and the amount of packet loss :-P Jokes aside this content was somewhat challenging at start, so many things could go wrong even simply with a series of bad pulls with too many statues with the wrong eyes at the worst moment. You still had a lot of freedom with the up to 18 people allowed in. I feel this content made it easier for larger groups than smaller ones. Some W2 bosses were arguably tough, Wave 3 had very steep requirements at start in terms of Accuracy needed, there were less valid options for DT/Hybrid sets for most jobs. W3 bosses presented some challenges but also gave you the option to make the fight easier by killing all Fetters. While ultimately made much easier thanks to the huge amount of new gear available (and now master levels) I'd say this can still be somewhat challenging for small groups
Odyssey Sheol-Gaol
The highest tier of this content is quite difficult, to the point some things not only haven't been beated yet, weeks after release (which is something I'd say unusual, given FFXI's history over the last few years) but some haven't even being attempted yet.
The content creates a more "controllable" environment by limitating the amount of players who can participate, disabling the freedom granted by subjobs and gating the content behind a currency used to attempt the fights (segments), which you can only gain in limited amounts, once per day.
There are incredibly high incentives to tackle this content on the highest difficulty, to unlock augments cap and to efficiently farm the high amount of points required.
The several limitations in setups required for each fight, entry fees, difficulty unlock and multiple "fuck off" mechanics give these fights little space for error and leave maybe too much in the hands of random things that the players cannot control in any way.
My personal take is that, thanks to the extremely controlled environment Odyssey Sheol Gaol is so far the "most difficult" content for FFXI.
They succeeded in making the hardest version of the content "desirable".
They succeeded in limitating the huge amount of freedom/synergy in the hands of players, hence creating content that's more averagely/regularly difficult, instead that the classic Black or White FFXI situation (where a content is extremely hard with most setups, but somewhat easy with a few others).
They succeded in creating this extremely controlled environment, without completely changing the core of the game (like WoW, for instance).
They failed in making, in my humble opinion, the content a bit too unaccessible (too many requirements, too many punishments, too many random/uncontrollable things).
I'm glad they managed to reach these goals.
I hope over the next few years the content will be progressively made more accessible for everyone but I don't see how they can do it given how there are no Job adjustments plans, ML is capped at 50 (and quite hard to reach) etc.
We'll see!
All things said, despite me whining a lot for all the choices they made for Odyssey, I can somewhat see why they made them and apreciate the fact they managed to reach this level of challenge.
Wish the content would mantain this level of challenge but with more reasonable/accessible requirements, but oh well, it is what it is.