I was gonna write an essay on this, but this should be obvious on its own by this point. The amount, or at least the ratio of jobs designed around procs is plummeting to the ground, and steadily so. I cannot know what they have planned for Dawntrail though, but seeing the pattern so far, let's just say I'm not having much hope.
Quick disclaimer: I do not consider "proc based" an ability that you activate from rotational mechanics (like DRG eyes, etc), and lights up after you do a specific sequence. Proc based in this post refers to rng based procs that light up and are NOT guaranteed.
So far the game only has one single full proc job, which is BRD. Full proc means that you don't have any base combo or facsimile of base combo, and BRD indeed doesn't have a guaranteed base combo. The second step (Refulgent) is chance based. Repertoire OGCDs abilities are also on a chance based and therefore (even if extremely predictable, which is appreciable but also boring), much like Refulgent, are standard procs in all the meaning of the word.
DNC, RDM are the remaining proc rng based jobs, but they're not full proc based, far from it. DNC has a baseline guaranteed 2 steps combo, from which procs are generated randomly, and unlike BRD and countrary to popular belief, DNC is less proc based even though it has GCD and oGCD procs. RDM follows a simulacrum of baseline 2 step combo, which is not a true combo by the fact that it has the dualcast mechanic behind, but in essence, you cast Jolt into Thunder/Aero, so in essence, it's a branching combo. You can proc Fire/Stone to replace Jolt, which is where the proc part of the job comes up, but it doesn't replace the baseline combo action. RDM however doesn't have proc based oGCD actions.
MCH used to be a full proc based job before its rework, since no step of the basic combo, like BRD, was guaranteed. One could say that ammo could help guarantee procs (much like Acceleration on RDM), so I could grant you that perhaps it was only 80% proc based idk. Either way, they removed the procs from that job for some reason. MCH didn't have proc based oGCD abilities though.
All in all, we now have a full proc base job (BRD), a 75% proc based job (DNC), and a 25% proc based job (RDM), and used to have a 75% proc based job (MCH).
Special mention to BLM that has procs, but they have been smoothed out of the rotational loop over time and thundercloud is the only one that still somewhat matters, but doesn't make the job really feel proc based much, but I had to account for it.
So while they remove proc based designs from ranged job and introduce basic combos into it (MCH), no melee whatsoever holds any proc design, and they keep introducing more of those, all based on positionals and basic or branching combos (branching combos also slowly dying over time, but that's another story). As a result, it means the amount of jobs keeps going up, while the amount of proc jobs is going down, or stagnating, resulting in a plummeting ratio.
On top of it, no support job whatsoever has proc designs, and all tanks follow a similar basic combo pattern while healers spamm one button. AST has rng in cards (which is nice), but it's not procs, with perhaps the niche mention of The Lord arcana, I guess. Worth noting even if it was very niche, DRK used to have actual procs with Dark Dance and Dark Passenger iirc (in Heavensward).
My question to the devs, if they even read this, is: do you plan to add more rng proc based jobs back at some point to the game? Or is this destined to be another dying model or confined to a couple of jobs like BRD and DNC?
On another note, I want to emphasize that the 50% (or lower) model is way more interesting than 80% + proc rates that proc all the time, provided you have enough different abilities to juggle with so that you don't die of boredom waiting for your ONE proc to... proc. But that's nitpicking anyway. I'm not gonna be picky as long as I have procs, and I must admit that I'm bored of constantly gravitating around the same 2 jobs because that's what I like, and I dislike combos. I'm slowly getting burned out of pve (vs pvp that is much more interesting in terms of flavor, uniqueness and toolkits), and perhaps it has to do with me being way too picky, so maybe it's a me problem idk.