FPS dips since season 7

As a beginning this is my rig: i7 6700k oc to 5ghz. GTX Titan XP 12GB 16Ram 2400 mhz. I have been getting less and less frames since season 7. I used to play the game on everything very high with 350-400 fps. Now i barely get 120 without any shadows and everything set to high instead of very high. I tried to use my friends old gaming rig to see how much fps i will get. (i5 750 stock, gtx 770, 8 ram). Well i got 100 fps with the same settings. What is happening with the game? a lot of my friends are experiencing the same things. My gpu barely gets used while playing. Like 20-30%. I have tried to update my drivers. Everything is up to date. How do i fix this thing? it keeps unbearable because in teamfights I get sometimes even 40 fps. I didnt buy this card 3 years ago just to struggle with league. I play every other game on ultra with more than 60 fps ( witcher 3, everything on, ultra 90-100 fps) and i get the same fps on shitty ass 2010 game that runs on my old pc with amd radeon hd 4650.