FPS Issue getting worse everyday

[Xerthus]

Oy, I'm getting a big issue with in-game FPS and I don't have any clue anymore. I have more & more FPS drops every day.

 

It doesn't come from my graphical card, as it runs last AAA games including Witcher 3 at Very High/Ultra settings. (And yes, the game uses the right card.) Plus, changing any graphical setting doesn't affect my DPS, even with everything disabled and 800*600 resolution I still have the same exact drops.

 

Before you provide a "fake" solution has I've seen thousands in forums :

-Game uses right graphic card, I don't have to swap it on Nvidia Panel

-Setting background fps limit at 60 doesn't change anything (and if it would, it would be REALLY stupid)

-Activating post-processing, motion blur + advanced motion blur doesn't help (And again this is a really stupid solution).

 

About my proc, I'm using an Intel(R) Core(TM) i7-4710HQ CPU @ 2.50GH and it goes up to 3.5GH. I'm running a lot of heavy cpu programs (formula with billons of data) and does some 3D render and never experienced a problem, yet the game goes up to 70% of CPU usage. My PC nor any component is overheating, memory is used up to 40-50% which is fine. 

 

So yup, at first sight it should come from the proc, but as I said, I'm running stuff & games which are more CPU Heavy, so what's up ? Really bad game optimisation ? Also, friends of mine who are playing all have an older proc (and slightly weaker)  and can all run the game with a smooth 60 FPS.

 

Also, I'm running the game on a windows 8.1, and again never experienced issue with any other game. I do NOT want to downgrade to 7 for many reasons, and not going to upgrade to 10 because of all issues with recent games.

 

Edit: Ofc I'm not running any program while playing except TeamSpeak, which doesn't affect since even when off, I have FPS drops

Edit 2: Forgot to mention, FPS drops since way more important while playing my Destroyer than my Sin.