Right now, I would say Last Epoch is fairly balanced for this stage in its development. You can play the 8 available classes and have fun. All classes are not equal, but in most games they never are. The developers also are responsive when things seem to get out of whack. Perfect Balance is impossible to achieve but a good balance can make a game that holds players interest for a long time.
Here is what I think of when I think of a balanced game.
KISS (Keep It Simple, Stupid) - A game should not require an encyclopedic knowledge to start, but as players gain more experience and knowledge about the mechanics, they will make better builds and better choices in gameplay.
KISS 2 - A game does not need 15 currencies and 20 different ways to craft items. That just leads to exploitation by those who know how to do things efficiently and those who get lost in the intricacies.
Not easy to overpower - A game should not allow builds that can easily overpower the mobs and bosses, or that has little chance of ever dying.
Strategy and tactics required throughout the game - A game should require some thought at all stages through the game and should not turn into a mindless button-masher.
Different objectives achievable - A game should allow players to choose different paths, whether it be speedrunning to high levels, item farming, or just a casual party adventure with a few friends. A game should allow the player to decide how they would enjoy playing the game.
What makes a game “balanced” for you?