Really, is there anything in this game that is truly difficult, or is it just punishing you arbitrarily?
This answer probably differs depending on class and role. Melee DPS play a different game than ranged. Tanks and Healers work together, but have an entirely different focus than a DPS. Casters want huge aoe pulls, melee cry at all the aoe that punishes them for their role and get upset at the tank for constantly rotating targets (since they have to to avoid the aoe). Ranged get upset when they are forced to move for a mechanic, and as a melee that's a large majority of what you do in a fight.
For this, I will use an examples in Bismarck, Ravana, or lower level content as very few are actually doing or capable of savage modes, and forgive me if I used melee examples more often as I believe encounters largely favor ranged, but more on that will follow. (You are welcome to make your own thread or post. and I'm sure you will make your own post saying why I am shit and you are the exception...special snowflakes...etc..)
There are a handful of mechanics that are difficult and require some skill to overcome, such as learning how to do Ravana's or Bismarck's phase transitions, but a large portion of them can be punishing.
A big example of this is the "HEY I'M CHARGIN' MAH SPIN" point-blank-area-of-effects (pbAoEs). While this is occasionally part of a transition, it becomes frustrating when these punishing effects are additionally hampered by latency and the fact that you must be touching the boss at all times, so dodging them becomes a 30yalm dash to safety, but you have to balance between participating in the fight and staying alive (how close to cut it). This becomes more frustrating to melee when they see a ranged class safely sitting at max range that just ignores that mechanic.
These frustrations are often magnified in between these effects when the boss randomly faces party members to destroy positional requirements for skills that again affect only melee.
Now, I know that many ranged argue that they have to move and do casts and this severely hurts their game play, but so do melee, every time the boss does an aoe, or a random aoe is on the boss, melee are forced to do nothing while they wait for the smoke to clear. Tornados (and some bosses) from bismarck and neverreap cause melee to literally stare at their target while it goes by constantly (higher concentration of players in one spot mean tornado target that spot more often) where as most ranged just dodge and go back to targeting from another safe spot.
If you want to talk savage, I only have specific experience with A1, and I will point out that resin bombs, adds (esp adds on resinbombs), and the randomness of missile placement can straight up wipe a fight just because you can't touch a boss. Yes you can compensate for this to some extent, but melee are a liability, if you could have a party of a smn, bard, blm, and a dragoon it would be ideal, and the only thing that would make it better is if you could replace the dragoon with a machinist if you don't need the melee lb or feel you need the piercing debuff.
It gets old, and I am sure I will get the usual comments of " ITS PERFECT, WHY DO U H8 YOSHIP," "Git gud," or or thinly disguised posts that's sole purpose is to piggy back a thread just to inflate their own ego. However, I believe these types of comments detract from meaningful conversations and distract from any meaningful message that developers may interpret. This game does have problems, and if you don't agree with me, you are free to say so, but specific examples as to why current mechanics are ideal would be appreciated.