with online games, there are a lot of variables at work that can affect your fps. The amount of players on a server, the latency of the server etc. With that being said, to make sure there isn't something wrong with your hardware, would you post your temperatures for your CPU and GPU specifically? Especially while the game is running. If components get too hot, they will thermal throttle themselves to a lower speed to preserve safe temps. You would perceive this as a decrease in performance.
Thanks for a good answer. I know my GPU runs at max 70 degrees Celsius. I am not sure about the cpu temperature. But last week the conditions were the same and I was getting high fps. I was chatting with some people in game and they said that the connection to the server wouldn't affect my FPS. but rather the lag.
To be honest the only reason I said that was because I play ARMA, and there is definetly a substantial FPS drop with more players in the server. I agree that it seems weird, but it's very true, at least for ARMA. You definitely want to check both your CPU and GPU temps tho..there is a lot of free software online for cpu temp monitoring
Just extract it with something like 7zip or winzip, and run the program from there. I don't know your hardware info, but use "RealTemp.exe" for 4 cpu cores or less, and use the "RealTempGT.exe" for 6 cores and up.
so I got... cpu -- 33 C under 30% load
Gpu -- 68 C under 74% load
I had my gpu overclocked to 1909 MHz from 1709. my memory overclocked to 2102 MHz. and the Gpu clock overclocked to 1706 MHZ. I dont know what I can do to get my 153 frames back. kinda pointless having a 144hz monitor if you are only getting 80 frames.