Synergy

[Shurrikhan]

As much as I love synergies, I absolutely do not want them to be along the lines of a specific skill interacting arbitrarily with another specific skill.

I'd much rather that there were further undermechanics and each skill's effects came from its undermechanics, which themselves could interact with others.

For instance, let's say Ninja were to make far greater use of its implicit Shadow resource and a Vision mechanic, which are themselves dependent on, well, a Light resource and a Line of Sight mechanic, respectively. Blind the enemies with... Holy, for example, and suddenly you've created an awful lot of shadow in a ring around them, too. Pair that with Spinning Edge (let's say, as an animation-appropriate AoE) and a Hide right when no enemies can see you, thus having affected all nearby enemies while blocked from line of sight and having entered stealth mode, and your Dream Within a Dream then duplicates your next hidden attack onto each enemy affected. (When every enemy alike just saw reason to think "Oh shit", and is wholly convinced they're about to be (Trick) attacked, who's to say they won't all be hit, given that you can summon shadow clones?

It's a powerful synergy, certainly, and Holy would technically be the best for the job, originally because it stuns (thus providing quite nearly the benefit of line of sight drops even without including the blind) and later just because it's still quite blinding, but Flare could do the job nearly as well, as could Verflare (or, if we wanted to really go along the Black/White magic theme, Verfoul, though as an attack coming from within the AoE, not duplicating outward, but --say-- massively increasing potency by a flat amount, as would be highly beneficial for a true AoE).

You'd thus end up with a huge number of different comps with fun names like "Black & White" for DRK, WHM, BLM/RDM, and NIN (or, if tanks were ever more than mostly passive mitigation meat shields, PLD, DRK, WHM, BLM/NIN), "From Shadows" when the emphasis is more on the NIN but the rest is flexible, "Tinker" for a comp centered on taking advantage of a MCH's excessively large (revised) bag of tricks, "Trammel" for BRD, DRG, GNB, and Healer (focused on stacking hit-and-run debuffs for a sort of semi-constant kiting supported by Swiftsong), "Guerrilla" for a RDM, MCH, BRD, DRG speedrun/ragtag comp (using DRG's damage-based-suppression and jumps as the front-line while crowd-controlling the rest into manageability via RDM and MCH), etc., etc.

• A Bard's running Swiftsong and uses Empreal Arrow across the same line by which a DRG is charging Doom Spike against a target --> extra range and the Doom Spike can now act as a blink strike, with the DRG riding his own aetherized into and through the target. (Same for Gyoten, The Forbidden Chakra, etc. -- any other damaging mobility tool or what could seemingly become a damaging mobility tool.)
• MCH detonates his Bishop turret, coating the enemies nearby in aetherized oil --> that next Flare on said enemies is going to a mighty bit more. (Or any other magical explosive.)
• If a Monk uses Earth's Reply to absorb a tremendous amount of magic damage, a SCH can just Galvanize that lingering aether instead of needing to apply their own to be Galvanized via Adloquiem. (Same for anything else that stores aether.)
• If a DRG uses Leg Sweep (Low) at the same time as a Monk uses Dragon Kick (High), that's double the chance of knocking the enemy prone. (Same for any other High-Low combo.)
• Pair a Full Thrust and The Forbidden Chakra (Monk's fiery uppercut) and enemies normally too heavy to launch can suddenly go flying skyward. (But, again, the same works for all skills with a Launch component.)

Again, the idea would be that each skill simply has a bunch of underlying characteristics which then interact with other underlying characteristics. While there might be a "best" skill combo to manifest that synergy, there are always multiple jobs capable of that type of combo and to nearly as great an effect.