Several people have asked me what makes Final Fantasy XI's combat "difficult". Thinking about it for awhile I've uncovered that choices have such an impact in the course of battle that the player has little room for error. This doesn't really tell you too much about the game though, so I am going to describe a few characteristics of FFXI's combat as well as some points of reference. This article will primarily focus on combat from a caster's point of view, but melee and ranged classes are also faced with difficult decisions. Abilities which temporarily boost damage output can kill an overzealous player if he/she pull aggro. There are jobs with positional abilities and combos. LotRO fans will recognize FFXI's Skillchain system as Conjunctions/Fellowship Maneuvers.
FFXI is slow. The whole game is. It is from a generation when MMORPGs were still worlds. Pretend that you are waiting 10 minutes for the boat to arrive in Mhaura while you read this (and then take a 12 min ride to your destination). Cast times, cooldown, and weapon swing delays are all several seconds long. All the spells in the Cure line (the quintessential healing spell) have 2 second cast times and 5 second cooldowns. Weapon delays are measured in frames, and the server runs at 60 frames per second. So a 600 delay Scythe has a 10 second swing time. And it will miss.
There is no natural HP or MP regen in FFXI. Resting regains these resources, but only after 20 seconds do they begin to tic upward. Resting is cumulative, so the longer a player remains resting, the more MP and HP is restored on each successive tic (with 10 seconds between each tic). Kneeling to rest and standing back up have animations which lock the character in place. Each animation is approximately 2 seconds long, and a player cannot move nor preform any action until they are completely standing. It is not possible to pop up instantaneously and toss a PWS on a critically wounded party member. Players must play with several seconds of foresight and judge when to stand and when to rest.
A Team Fortress 2 friend of mine (Hi Polonius) says that he enjoyed healing in FFXI the most out of every MMORPG he has played because of its difficulty in judging when to rest and when to actually cast those Cures.
The game is filled with tiny nuances in play like the resting animations. The player is technically still resting during the standing animation, and it is possible to get a final tic while straightening up--a skill that requires impeccable timing. Even to chain cast spells one after the other, the player must learn cooldowns and casting animations. Using animation hints like these makes the game feel like a Fighter at times. There are many more places of mastery than just animation hinting.
Buffs and debuffs are immensely powerful; so much so that there is one class dedicated to them: Bard. Debuffs on mobs increase the effective HP of the tank and the DPS of the damage dealers. They can make a party extremely efficient, killing for 3 hours without stopping. The Red Mage's repertoire of white and black magic (particularly buffs and debuffs) as well as some Red Mage onry buffs make it perhaps the most powerful solo class in the game (as 75 RDM/Ninja).
Red Mages also get FFXI's only set of pimp gear.
Some may point to WoW's buffs/debuffs. I will agree that WoW's debuffs are very important to the group or raid, but how many players bother to stack Expose Armor, cast Curse of Elements, or even Judgement on trash mobs? Parties burn through them so quickly, it isn't worth it. Even while leveling or farming, unless the player is fighting a mob of +3 levels or an Elite, she would be more efficient to just do damage. Most of the experience parties in FFXI take 1 or 2 minutes to kill a mob. That is plenty of time to reap the benefits of status effects. Debuffing also generates tons of threat even if the spell is resisted. So if a player casts 3 debuffs and then immediately starts a nuking rotation, they should prepare to pull aggro.
Perhaps the consequences for failure in FFXI artificially make the choices seem more important. This may just be another lesson in risk aversion, but the other side of the spectrum seems to be Achievement frenzies, and personally I'd rather have risk-reward cycles. If I die in FFXI, I lose experience--the question is how much. Becoming "incapacitate" removes ~10% of the experience required to level from your current total. E.g. I have 802/10400 EXP. Dying would remove 880 EXP, dropping me to -78, at which point I would delevel and be at 9122/9200 EXP. I can lie on the ground for 60 minutes until I automatically return to my homepoint. If someone casts Raise on me, I will get 50% of the lost EXP returned (440), and be restored my level (leaving me at 362/10400 EXP). Raise 2 will give 75%, and Raise 3 will return 99% (but is a level 70 White Mage spell). As anyone with any insight into death penalties will say, this is simply a loss of time. But it stings. And letting party members die might label you as a lousy player. The reputation hit in a group-focused MMORPG is more severe than a few hundred EXP.
Bunch of us eating dirt.
By now I hope I've illustrated how little room for error there is and the punishment for failure. An unfortunate characteristic of RPG combat is the reliance on gear. I've heard players say that FFXI is 10% gear and 90% skill, but I find that breakdown to be very off. Melee damage dealers without Accuracy gear will miss. No amount of skill will make that Random Number Generator be nice. The same is true for debuffers who will want to stack Mind, Intellect, or Charisma respective of the spells they cast. Most of the time, players can get by with the cheap versions of this important gear, and perhaps that is what the 90/10 comment was referring to, but there is a noticeable difference between someone with cheap gear and someone wearing a few million gil.
One more thing I will mention is that Square-Enix is very secretive about mechanics in FFXI. I call it a Hidden Information policy. Nine years since FFXI came out, the developers have never actually told the players what stats do. Players have experimented and inferred what purpose Strength has, for example, but I doubt we will ever know the full extend of STR's influence (certain weapon skills receive bonuses from different stats).
Even though FFXI's combat is slower paced than most moderns MMORPGs does not mean it is boring or uneventful. On the contrary, players have time to think and make important choices. Because players are not simply reacting to stimuli on the screen as they would in a faster-paced environment, the developers have created little room for error. Fewer actions are executed in FFXI than in WoW, but each one of those actions (or inactions) carry immense weight and could mean the difference between 10k EXP per hour or losing 45 minutes of your time.
And those of you who like WoW Talent theorycrafting, look up a subjob discussion. There are 362 job permutations in FFXI, and players can change gear while in combat.
Here are some videos of experience parties: