Proc'ing is pretty lame and shallow to me. It's like being the unpopular kid in H.S. who isn't very well liked, but has a car. No one likes you, or even wants you around, but you have something they need, so you're tolerated.
Instead of worrying about job specific procs, I feel that leaders should be concerning themselves with filling positions.
I understand what you are saying and you are absolutely correct with your analogy, unfortunately, that's how the people in FFXI operate. People max/min everything. Take the main healing position for example. WHM was always a better healer for anything that didn't have a short timer, but RDM always got the spot simply because of refresh. That's how the population thinks, "if it isn't the best, then it sucks". So, the only way to force people to allow other jobs to play is to do proc's, else those jobs will never be invited.
Look how people max/min the 4 person party for NMs? People found and created ridiculous job combinations, i.e. BLM/brd, in order to max/min their game time, completely defeating the purpose of procs in the first place. Unless you force people to invite you, you simply wont be invited. So, you have two choices, either force the game mechanics to employ you or hope the mindset of 10 years of game play change.
All of this should be needed. Since every single job in the game can fill at least one of those 5 basic roles well, there's no need for artificial cooperation (procs).
But if you must have procs, have procs based on the holy trinity. Start with the NM in "X" form having incredible attack speed/power, but limited to single player attacks. You survive without dying, it's a proc (Possible to be evasion tanked by extremely evasive (3) jobs and gearsets plus evasion buffs, or a turtled up PLD). (The DDs are holding back and saving TP and you don't want DD tanks, since the healers will need that mp later.)
After the initial proc, the NM changes to "Y" form. It must take a certain amount of damage in a timeframe to get the DD proc. (Time to buff up, weaken its defenses, and unload those nukes and TP you've been saving. Additional damage from MB.)
Finally after the first 2 procs are met, the NM goes into mini rage mode. Its attack is increased and it gains access to potent AoE abilities of 1 element. Survive with no deaths in this mode, and the "Z" proc is met. (Recommended for buffers to switch to defensive buffs.)
Now instead of individual unique procs, any job can contribute to the procs in their own unique ways. You're no longer waiting to fill a spot with a certain job, but instead, you're looking for a role to be filled.
That sounds nice on paper, but it wont change anything. People will invite every job for a few weeks, then they will max/min it like they did in Abyssea and jobs will be left out again. You only have two choices to guarantee everyone's participation.
1. Give every job very unique abilities and spells that are "game changing", i.e. haste, refresh, etc.
2. Give every job unique procs.
The ideal situation would be option one, but that will turn out to be a very difficult task as you get to the 6th DD job. After so many DD's and mages, people will just weigh the abilities and just start accepting one over the other. Giving every job at least three unique procs at least give you the tolerance to join, which is better than wishing you were in a party.