You also, as I did, have high GPU usage and bad / mediocre performance? Well, this is what i did to fix the issue. It might also work for you.
1. Open the game.
2. Go in Options > Graphics
3. Look for “Antialiasing” option
4. Set MSAA to 2x, or disable it if performance still is bad with 2x.
Explaination of why this works
The game BY DEFAULT sets MSAA to 4x.
MSAA is not your average type of Antialiasing but a rather old and extremely inefficient antialiasing method that uses “supersampling”, which basically increases the number of pixels by a multiplier (2x, 4x and 8x) pushed through your graphics card to get better image definition (remove jagged edges).
This means that if you put MSAA 4x the game will be rendered FOUR TIMES instead of ONE by DEFAULT, and this is why it’s so damn heavy by default. Even with my GTX1080 8GB, i had an insane 80% usage on 1080p resolution!
But after putting 2x or even disabled, as you prefer, the consumption dropped to not more than 30%.
I hope this works for you, but if you run the game a toaster don’t expect miracles, of course there are technical limits!