So Let me say this and this is the true cold truth... balance is almost never a problem on games that use "mmo tags"
First off, people will play whatever they enjoy you don't have to nerf or god mode the thing to get people to not play or to play the job.
Second: the reason Balance isn't the issue is because the abilities are not the problem with the game (yes, you might say this or that oh its not strong enough or its 2 strong) that isn't the problem.
Third: The real problem is how bosses and monsters are made... they are a 1-2 on normal monsters Ability set revolved around hp%
Now what should be done to solve the real meat of the problems with how things are.
First: stop crying that it's a balance issue it's not
Second: realization to not make things really so dumb a monkey could do them.
Finally: Invest in an AI that doesn't focus on the machicas like DPS Check or Healer check or tank buster, but an AI that focus on destroying the party.
Next:Bosses should be made to kill the party not to be a challenge, but the boss should have an AI program that is extremely Op that will flat out kill people.
What does this mean?
Simple: some fights should be made to target the heavy hitters over the tank
Put yourself the maker in the bosses shoes not the players (putting yourself in the players shoe on the fight causes so many failures and lameness and you should feel ashamed of doing it that way) What happens when you put yourself as a player you go well Cool music check, Cool images check, cool art check, cool boss look check, Intresting Mach looks check. While the boss themself is basicly that one idoit in class doing everything they been told without thinking for themself.
What needs to be done:
1st remove equipment durability (this is a must so people don't cry oh, I died, I gotta repair) (this leads to fights being dumbed down because of the players themselves) 2nd: Bosses with Target commands that will go outside of the tanks to attack the heavy healer or heavy DPs user and if they aren't protecting or handled in a quick taste, the guy/girl dies and will need a race (this right here solves 2 birds with one stone) 3rd: Add an ability to some of the fights called dispell or some incurable slow/stop.
4th: bosses with lock out abilities or Kill for AP 5mins of the
5th Bosses that uses abilities at random and throw in some secret coding of abilities, it has without being a magical like give Ultima the ability to cast Ultima randomly without a cast timer on the group and make it a 1%-5% to happen 6th: bosses need to have a 1-5 roll on them so every fight is different on the boss, maybe effort will have fired on one fight, but on the other has flare basically give the fights a random gen so its not about reading or watching someone else information and teach people to play with their own skill
7th: Fight counters: so basically give fights abilities such as zombie : So for healers if your team member has zombie on them and you heal them they die, mags if the thing has firewall don't use fire or it will heal.
The basics: it's not that things are not powerful or they are 2 powerful its the fact the game has no AI to counter anything you do and there's not a damn thing your nerds or removal can do about it, something will always be"powerful" and something always will be "weak" so use a damn AI that is worth something.