Hello Everyone.
This Guide is for everybody with low end PC and has FPS issues with the game.
I play personaly Titan Quest Anniversary Edition sometimes on my 8 years old laptop. (weak pentium and GT 525M) and the game runs around 30fps on average on low details and 1366x768 resolution. So enough talking and lets get to the point.

FIRST OFF ALL: THIS GUIDE IS NOT 100% BUT IT WORKED FOR ME AND FEW OF MY FRIENDS.
The guide is simple.

1. Go to your steam library and launch the game via "Play" button.
2. Next in the dialog click on option "Launch Titan Quest Anniversary Edition (DirectX9).

3. And its done. The game now should run much better. For example it doubled my framerate to stable 60.
Thanks for reading and let me know if the guide helped you !