I did 15 run and found 1.
I've been lucky!
how many run have you done? 

im on 20 now and got 2, sadly 2 awful ones too haha.  Running fk20 btw so its takin like 2-3 mins a fight for me im not that overpowered

There are 9 different artifact sets at FK. The normal chance is 1 of 9, the actual chance is 2 of 9. 

2 out of 20 is bad luck at a very small sample.

P.S.

Jeri Ryan thinks the chance should be Seven of Nine. 🖖

I don't farm unless in champion fuse/fragment event because they all drop shyt.

i´ve got 0 after 20 run

Simply put, small sample size. The probability of getting zero after 20 runs is 1 - (7/9)^20 = 99.34%.

Yes - that's certainly a very high chance. But it's not 100%.

oh yes, the math will show us how wrong we are

I saw another discussion along similar lines about odds of pulling a lego.  It seems that the chances Plarium gives to get certain things do not apply to any one account.  Rather it applies to the whole population of players.  So what any one person can expect is totally up for grabs. 

The discussion was about someone that claimed to open 319 ancient shards and never got a lego, even with their claim about having a safety net.

https://plarium.com/forum/en/raid-shadow-legends/674_game-discussion/240321_319-blue-shards--27-epics-and-0-legendaries/

And the person who opnened 319 ancients just pointed out that she used different accounts for doing that - what makes the whole thread a kind of [BEEP - insert harsh word here]. Of course the mercy counter is bound to the account and not to the person. How should that even work? The algorithm doesn't know that your second account belongs to you.

It's still rng at the end of the day, the odds of getting a particular piece from FK or any dungeon for that matter are small. Double chances for that specific piece is a nice boost, but not as big as people may think. Over the course of a lot of runs you should see an increase in Stun gear as opposed to how much you'd get without the double chances being turned on.