Looking for some help with dex stacking ballista build

Hello,
Premise this isn't a build guide, it's my first dex stacker, I just browsed a few builds on poe.ninja and tried to make it work as I could.

Here's my current pob: https://pastebin.com/CkaK5nup

I'd appreciate if anyone would be kind enough to guide me as to why my build just performs really awfully both in terms of dmg and feeling good to play.
I'd really like to understand how to make it work for sanctum as that was my original goal.
Yes most gems are still not fully levelled yet but it doesn't feel like that'll do too much for the build.

https://www.pathofexile.com/forum/view-thread/3210813