Low FPS/Shaky mouse on mac

Here are my system specs: Macbook Pro Retina (Mid-2015) 2.5GHz i7 16 GB RAM AMD Radeon R9 M370X 2GB

For a long time, I had been having issues with my mouse jumping around, essentially making the game unplayable. I solved this by turning Software Mouse off, but now I'm suffering from gigantic FPS dips during fights. I've tried bringing the graphics settings down, but that doesn't actually seem to affect it; and besides, I should be able to run the game at max settings with my computer. I've looked for solutions online, but I don't see anything recent, and they all involve turning off V-sync (which I've done already) or turning software mouse on or off, which just replaces one issue with another.