I'd say there are teams that can't beat the game, but one guy beat Shinryu and maybe Neo-Shinryu last year with one knight and 3 berserkers.
No matter what modifiers you put on, you're guaranteed at least one of the wind crystal jobs and all of those can solo the game. The damage output from the triple berserkers even makes the hardest runs (WM and thief) a bit less tedious.
Cower in fear.
You know, I'm sensing Irony right now.
To be honest, it hasn't been that hard so far. BM is one of the easier solos, and the few fights that are normally tedious due to magic immunity (i.e. archeoavis' undead form) get sped up by the berserkers. I might have trouble with Shinryu and Omega, but beating the game shouldn't be too hard.
I still don't get how Chemist is supposed to be so overpowered. I guess if you grind for dragon fangs, dark matter, turtle shells and enough gil to buy 99 of everything ever, maybe? But it really seems like everything would burn through items fast, and fights would take too long to start doing serious damage.
Some of the crazy game-breaking stuff requires farming for turtle shells/dragon fangs/dark matters, but you can usually save those for the toughest bosses. Even regular healing items can give you stuff that's considered "best ability" for other mages.
Use this chartWith just basic world 1 restoratives, you've got
Level +10 (can stack)
Unblockable berserk
Absorbing fire, ice, and lightning
Full HP revival
Revival with full MP restore
X-Potion
+50% magic attack
Float
Confuse
Then you factor in all the cool stuff drink does (drinks can be bought for ~100 gil early in world 2 and you'll collect a few in world 1).
If you're willing to farm dark matters you can solo Shinryu and Omega, with the backup of a FJF party you don't even need to do that. Chemists may not be flashy or have easy to use "press A to kill enemies" abilities, but they've got the best support abilities and a way to wreck every enemy in the game, and no other class can say that.