So I noticed something very weird yesterday: maybe my issue is something different. When a 4v4 match loads there's the "face off "screen where all the 8 heroes are standing in front of each other and after a few matches I suddenly noticed my frames go down to 25-30 whenever several heroes are shown together on screen, be it in the match or that loading screen. So I lowered everything to absolut min under the graphics option to make sure it isn't jsut my system that's to weak but it still happened. Then I restarted the game and lo nad behold, I got my 60 frames on high settings again. A match later, the stuttering was back.
I tried to make screenshots but unfortunately the Nvidia overlay doesn't show on them.