My only problem with any situations like this is flat out, The jobs should be unbalanced.
Going in contrast to what Sneaky said, certain jobs need to have certain merits based on thier functionality. Finding a middle road is a foul. Homogenization is the bane of all gameplay. There becomes a point to where you basically play a job soley on asthetics... Because all the jobs have the same potential.
In my opinion, SE should make stronger distinctions between the classes, and go back to thier roots, making areas with mobs that are conducive to certani party settups. However, that would have to rely on the players not being tools.
However...
Hell is other people.
No matter what, you will end up with a floating crema of expertise, and that's what settled at the top. Certain jobs had thier Field expertise. Like Sams were used in LS for Skillchains on HNM, Blms, were used to nuke those Skillchains, Thieves were used for soloing and TH in HNM, etc...
All the 'undesired' jobs were used for meriting. Monks and Wars got thier share. The only problem with this became, that Meriting became 80% of the game after a while. Mainly due to wear, and people having thier stuff, and Items being worth jack shit. But to make that arena open to all the other jobs for the sake of "fairness", it's Bullshit. Should there be a bump? A nudge? Sure. But what would be a logical way to do said bump?
Imo, you need to analyze the classes for thier merits and redesign areas to better suit them. I.E. Make areas were demons/imps/squids reside for Sam parties, to take advantage of thier job traits and Slashing bonuses; while not gimping the EXP. Make the spots pretty specific and rewardign to those job classes, while a detriment to others. Make "Ink Jet" and "Hecatomb Wave" really severe blind(Ink Jet already is) and make it require multiple Blindnas, like Mortal ray requires multiple Cursnas, and in the process make Sams' 'resist blind' trait really strong. The only job currently that has the proper model for thier effectiveness is monks.
So if SE really wants to make an "Adjustment" they should ajust the game dynamics smarter, not try to make all the jobs alike.
One of the things that woudl have made more sense, would be to make areas where mobs were weak to G.Axe "Crushing Damage", while making trolls weak to crushing, and increase the damage bonuses on GK, and Scythe, and Pole for Slashing/Piercing respectively. That way if you did trolls, yoru war would do better as a G.Axe user than a Ridillberk, and Bird camp would be better populated by Drgs than monks. Send the monks to populate now barren Bone camps, and reformulate the fauna around the shipwrecks to give Sams and Drks a place to play.
THAT would be an adjustment.