I bought my gpu 2 weeks ago. I don't overclock much.. I'm contented adding +50 to core clock and +200 to mem clock. That would be 0 for mv. 
There's a camp in witcher 3 when I throw grenades to the bandits, explosion of artifacts came with it. So the smoke effects must have something to do with it.
So I to reset to factory clocks to see if it goes away, but it's still the same. 
 
My questions: 
1. Is it the witcher game having the issue with the artifact since it only happens in a certain place?
2. does it mean i have a bad card? (asic 71%) so bad even in factory clocks, still artifacts shows?
3. can i just ignore this and stay with my desired overclock and somehow the artifact will not damage the gpu or it's already damaged that's why it shows?

I didn't try to down clock it. Only the factory stock clocks. Because I don't see the point of down clocking a gpu that has been modified to run in overclock (ftw+)
Just to play it for stability sake.

Okay, thanks for your suggestion. I will try it now. 

I'm not super techy when it comes to troubleshooting, but if you have another GPU you can test it with and it still happens, I'd guess it's just the game. I don't know of another way to test if it's the game.

Is this the only game you see artifacts in? If yes, then it's most likely just the game.