I fixed most of the screen packet traffic in #1866. However, there's still a lot more room for improvement:

1. Don't send hover data if the module being hovered over doesn't use it (can't do this now because we only know this by whether the server-side module implements ITooltipInfo)
2. Either let what's being hovered over inside the module be figured out on the client, instead of sending every x/y to the server, or group the x/y with messages that already have to be sent anyway
3. Somehow tie what's being hovered over to players, so that two players at once looking at the screen doesn't break everything
4. Don't send hover data at all if WAILA/TOP aren't installed
5. For TOP, let the server figure out which module is being looked at from x/y (can't do this now because modules' heights are only known on the client)

Subpoint 4 is completely fixed. Subpoint 3 is fixed for WAILA, but not for TOP.