Build balancing is not good. Options are too limited for end game.
You really do need specific build/class to do high level nightmare dungeons.
Instead, it should be about optimizing your build, to get there.
It really limits the games content, funneling everyone into a few viable builds.
Why even have the other builds?
I know this is redundant but, you can watch youtube videos where they rank builds by tiers.
This is a gameplay design where you limit your own content, not smart.