I was trying to think of various ways to increase difficulty and this is what I came up with:
- Increased stats: more damage dealt and a tighter DPS-check. Think T13. Odin on a casual level.
- More dodging: compare Titan HM to Titan EX… many people thought HM was somewhat intense when it was first released… until they saw EX.
- Team communication: things like Ramuh EX or T2 without the enrage strat, T10, T11, T12… these fights require people to talk to each other or at least delegate responsibilities and priorities ahead of time. Moogle EX requires some delegation of responsibility and communication on where to stand and which mobs to focus on at any given time.
- Individual responsibility: stunning, silencing, kiting… things like High Voltage in BCoB, Renauds in T7, or even Ifrit HM at launch. Chimera actually required silencing, stunning and kiting orbs before people used the terrain exploit. Machinist might have some new debuffs or CCs given what we've heard about targeting monsters' body parts.
- Unique debuffs: Leviathan EX, Ifrit EX, and T8 do this well… there's plenty more they could play with, like Pacification/Amnesia, Terror, Doom, Zombie… Mahisha S Rank and Qarn nightmares. World of Darkness did this a little with Doom and Death, obviously on a casual level. The opposite of this is unique buffs. The Chrysalis has a bit of this, and from what we can tell Astrologian is going to bring some interesting new buffs.
- Weaknesses and Resistances: T4 knights/soldiers used to be resistant to either magic damage or physical damage… Leviathan's head and tail reflect different types of damage, Agrippa The Mighty S Rank… T2 used to favour different types of dps depending on which path you took... They could also have weak spots on the boss that required attacking from certain directions at specific times or exposing weaknesses by using specific skills and spells on their own or in combination with others.
- Resource management: there are certain jobs that risk running out of TP or MP faster than others, like MNK or WHM, but a fight that required all jobs to more carefully use their resources could up the difficulty. To some extent T4 did this because you had waves of enemies where AOE was used by the DPS, the healers and the tanks, and even enmity as a resource could become an issue as the tanks would race to grab things as they spawned before the healers or dps could take hate. New abilities may help with this a bit, in the way Goad has done. Dark Knight seems like it will be an MP, TP, and enmity management job which could be interesting.
- Puzzle elements: things that have to be placed or done in a certain order to prepare for upcoming mechanics. Crystal Tower does this a lot… Scylla's orbs, Behemoth in LoTA… T8, T9 do this with towers and meteors…T12 to some extent with Bennus. Ramuh EX does it with orbs. T2 tried to do something interesting with this idea where you would disable certain abilities and grant specific buffs to the final boss depending on which mini bosses you killed on the way to it. Diabolos doors... Vishap did this on a very casual level.
- Instant death mechanics (everyone's least favourite): Titan, Qarn, T5, T6, Demon Wall, etc, etc.
- Randomness: This can mean a lot of different things… it's also likely to be the most frustrating and can also be the most detached from actual player skill unless it's executed properly. Bad phase changes in T7 are a frustrating form of RNG. Simpler forms like Ramuh EX lightning rings, T5 and T6 markers, etc. are a bit too basic. Shiva EX plays with the idea of randomness a little bit and is done fairly well. Savage Coil uses RNG a bit more… like in T6 where the bramble patches can appear anywhere.
I could probably go on, but these were the ones that came to me now. The point is they can always just pile on more in any individual category or combine them in new ways. The skill cap will likely increase up to a certain point where it just becomes unreasonable for a normal mode raid and anything greater will be relegated to Savage mode… where the real variation will come, especially for the expansion, is using new skills from the levelling process and new combinations of mechanics to force people to play their roles in a slightly different way (Ramuh orbs for tanks, kiting Renauds for ranged dps, Leviathan EX for healers, etc.).
There's quite a lot of variety already in FFXIV and I think there's a ton they can do. There's doubtless a lot more that I haven't thought of that they likely already have planned!
Yoshi-P has said this about new abilities in Heavensward:
Please look forward to it.
Also...
If I have the energy later I might put together a shorter list of quotes here of all the brand new things being added in the expansion and all the significant changes to existing systems they have planned as I realize not everyone follows the interviews and stuff as closely (Sho's extensive list is great for this too). And because:
http://imgs.xkcd.com/comics/ten_thousand.png