Massive FPS drops on MAC

Since some time when I am playing LOL on my macbook pro I am experiencing massive FPS drops especially during teamfights. The game is basically unplayable for me on my laptop now and its pretty frustrating. I tried all the troubleshooting tips in the boards but the fps stays between 30 and 60 all the time. I did not have any problems with this before on my macbook and it looks like a bug. It started when I patched some time ago. Is anyone having the same issue and did you find a solution?