Trying to figure out how people get insane damage with characters.

https://preview.redd.it/5ahlv0crboee1.png?width=2000&format=png&auto=webp&s=03d3141f0dd2856b2858b504ae75e0946d7748a9

I've got tons of characters that I grind to hell for and max out everything and feel like I'm doing poor damage.

The Herta being the most recent on my list of failures I hope someone would give me some advice on what to do with my current build.