hello,  me and my wife are experiencing the same issue randomly. just letting u know your not the only one . both of us have desktops. my specs are i5 7600k, 1080, 16gb corsair rgb pro, and running on a 1tb m.2 ssd. her specs are a ryzen 1400x, 1050ti 4gb, 16gb ballistix, and she also has a ssd. I may or may not have found a fix but went in to my nvidia control panel and manually turned on my vsync turned my gpu to my 1080, and turned it onto prefer high performance and restarted and haven't seen any artifacting as you see in your pics as of yet since ive done this. try that and see if it fixes it. mine or hers didn't do it all that much to begin with but when it did, it was on certain levels or spells or abilities being used as you described.