I am on older hardware (5800x3d/2080ti). I have always run windowed fullscreen (to make it easier to access the second monitor). I set 140fps limit for my 144hz screen, I can easily hit 160-180+fps with my in game settings. Until EoF, its always be super smooth. This season, has been a choppy, stuttery mess. I can feel it drop frames and effect input latency... my FPS stays steady at 140, but it feels like im dropping down to 10-30 FPS momentarily repeatedly. I may try a different PC with a 7800x3d/3070 and see if its any different, but I only use my current system for D2 and changed nothing. The latest update did not change anything for me, better or worse, its been that same way as you describe since the launch. Sometimes I cant even shoot my gun when I pull the trigger if tap firing... miss jumps, slides, etc... Happens in both PvE and PvP, and has ruined flawless runs through activities.