Unfortunately this is built incorrectly because Luminari Regalia is not a Pierce set but Elemental.
It has ~75% Piercing to Elemental global conversion that ***** you up. Also Luminari Sidearm has mostly Elemental damage here.
You need to redo the build completely to Elemental for it to make sense if you want to use this set.
Rozumiesz po angielsku? 
Yes i understand
Here’s an example of a example of a proper build (also very optimized) by 
@mad_lee
https://www.grimtools.com/calc/0V0a7AyZ
He built it as Elemental because the conversions on the set don’t allow Piercing really.
@Monkeyking I mean I can see you build characters well it’s just that this detail which is Pierce to Elemental conversion ruins otherwise a nice build.
Post how your build performs. There are many common parameters by which builds are gauged, including boss kill times, Crucible clears and Shattered Realm Shards reached. If you want tips, I’m sure veterans of the community will help you out!
Don’t just post GT links, you did they same here Luminari melee tactician
what if you used the conversion to make it into a weird hybrid damage build?
https://www.grimtools.com/calc/YNnrmjwN
Then mad_lee would comment on it and both of you would get banned 
Seriously though, I get what you’re saying. Technically it’s not incorrect, just sub-optimal.
The design intent of such a “dual” set is probably to
- make it less obvious
- for the leftover Pierce damage no to be infinitesimal
- well ok let’s say sub-optimal hybrid builds
- and probably most important - give options if you’re not using the full set
just jacket + gun for example with full Elemental to Pierce conversion