I'm not going to play along with the idea of age, job, and income, but I will note a few things
I agree that a few things are cheesy and could be better balanced, but for the most part I ignore them (and it's not like BG I and II weren't full of cheese and imbalance. I recall reading about veritable fountains of fondue being present in those games, ready for people to take advantage of plus the whole buff yourself to godlike levels then wade into battle that can't be done in BG III). For me balance has a specific idea behind it, that I will explain below (and quickly note that if one class only does one damage, while another does 100, game balance has been thrown out the window and trying to balance around that is ignoring the real problem).
My opinion is that, in a class based game, all the classes should have an equally difficult, equally rewarding experience, or at least as close as reasonably possible, without making them play too similarly (I'll focus on single characters for the moment, as that's much easier to come up with solutions for). Let's take three hypothetical players, playing three different classes. Finn the fighter, Mark the mage, and Theo the thief and see how we can balance those three playstyles in a turn based encounter with ten initially unaware enemies (well, balanced to my mind)
Finn has the advantage of being a durable SOB, but has to avoid be overwhelmed. He goes in with a charge, and takes out a foe. Now he has nine angry foes attacking him at various ranges, and needs to figure out how to take them down. Obviously he needs to prioritize the most dangerous foes, and the squishiest. He has several abilities that allow him to close the gap and avoid getting surrounded, but they're semi-situational (IE need to be used at the right time) and can only be used once apiece. Obviously, closer ranged and tougher enemies would do their damnedest to prevent that so he would need to figure out a way around them, and there should be several way to do so (knock them back, find a way to go over or through them, stun them, etc.) but with downsides to make their use a bit more risky and encouraging smart planning, lest he get overwhelmed and unable to kill the real threats. Once they're down he could take on the lesser threats, though with some care needed not to be overwhelmed.
Now Mark would operate differently. He's squishy as heck, but with several powerful spells to turn the tables. He could start by casting a fireball in the room, eliminating one or two and weakening at least some of the rest, but now he has several angry foes out for his guts and he needs to keep them from outright killing him. Remember, he can't wade into the heart of the foe like Finn can. He needs to stay away from them. One option is to kite the melee fighters while taking out the real risk that are the ranged fighters, but it would need to be handled carefully, lest he get himself cornered, which would result in a quick death. Once the ranged fighters, who he couldn't kite as effectively are gone, he could focus on the melee fighters while keeping up the kiting, though still with the risk of making one mistake and finding himself cornered and slaughtered. He could have a few abilities to help deal with the changing situation, but again, they would likely be single-use and have to be used at the right time.
Finally, Theo, whose durability is between Finn and Mark's. He plays rather differently to the other two. His best bet is to pick off individual enemies quietly and without the rest noticing. Of course, if they can notice the corpses (let's say they can), Theo might find himself in a world of trouble if they start investigating. If they do find him, he is indeed in trouble, though not necessarily as much as Mark. He can fight back and survive even if foes get in his face, but only for so long before they slaughter his ass. His best bet is to get back into stealth and get back to picking off the enemies one at a time, though now at a disadvantage, as they're now aware that he's around. He would have a few ways of doing this, though they would rely on breaking line of sight to pull off, which could be challenging now that the enemy knows there's someone here picking them off one by one.
In a well balanced encounter, they would be able to strategize, find a way to take out the biggest threats, and all in all keep themselves alive, no matter if it was Finn, Mark, or Theo. And there would be multiple ways to go about it, some more challenging and dangerous than others, perhaps, but still viable and rewarding. In a poorly balanced encounter, one of the three would be able to walk over the enemy without issue (say Mark's fireball killing everyone) while another would be flat out struggling to get anything done without a very precise strategy and perhaps even luck (Finn, for example, needing to attack foes and use abilities in a specific order and have the random number god smiling on him to succeed).
What it ultimately boils down to is that, unless they're specifically marked as such and designed as such, I don't want specific classes being far easier to play the game with and other far harder to. I want my own stealth and backstab-heavy playstyle (The Theo style described above) to be just as viable and rewarding as a straight-up fighter's in-your-face, engage the enemy directly style and a mage's magic heavy, keep your distance, burn them to the ground style, and both of those styles as viable as each other. I hate the idea of "oh your favorite class sucks, and when you pick it here the game is going to be ridiculously hard for you, whereas if you picked this class that you may not like at all, it would be a walk in the park." That is a sign of bad game design.
