Ahh, the amount of players is a huge factor.
As I join servers with less than 10 people or play with friends most of the time (2-3) I get FPS because of that. I joined KOTH once and admit to have dropped around 30 fps because of that.

I saw your arma post on the weapon mod and how you said you were getting 60 fps. I have a gtx 970, amd 8350, 8 gb ram, and running on an SSD while getting 10-20 frames on a heavily modded server with about 50 people on. When playing KotH, I can barely get to 25 fps, same goes for wasteland and other vanilla servers. My specs seem to be just a tiny step above yours yet mine are performing way worse. $1.3k :(