You say this, but when I used to play CSS years ago, I think it may have been a Q6600 with 4950, I used to get a solid 300fps.
Yea but GO is a different game,the framerates just get worse after most updates from my experience.All the skins ect just add to the load on the engine.
On one of the operations last year i was even seeing the fps on certain maps dropping to the low 100's in specific areas.
You aint really gonna see any tangible benefit upgrading your cpu,unless you get a new mobo and a haswell CPU.
I do understand why it irrates you tho,its not even the framerate per say but when it tanks,the frametimes increase and you can feel that.