I have no idea what the problem could be, but there is a lot of stuff you can fiddle(sticks) with.
Have you tried fiddling with the v-sync and framerate cap settings?
fiddle with Borderless / fullscreen?
fiddle with effects details? In teamfights all the abilities and their effects get popped, if effects are the culprit then maybe there's a problem with effects rendering.
Put everything on max but effects on very low and see what happens.
What is your monitors refresh rate? EDIT: 60Hz, just saw.
If you try capping framerate, put it at 60.