It is true that perfect balance is impossible in any game, single or multiplayer, but there is a difference between trying and not trying. The balance delta should not be such that people feel penalized for their choices because one class makes the others seems like separate game difficulties. There's a reason even DnD comes out with new editions, as does the Warhammer rulebooks and other tabletop games, as well as modder balancing out single player games.

The whole point of gameplay diversity means having really competitive choices to experience the game different through gameplay. Developers should strive to get classes as close to power level as they can. They have loads of player feedback on top of player metrics and data to sift through their published games, there's nothing wrong with updating their games to even out the player experience across classes.