On my mediocre laptop (i7 2670QM, 8Gb RAM, Geforce 555M)I'm having performance problems in multiplayer. Here's an example of GPU&CPU utilization in SP and MP;

My game settings:
1600x900, 100% resolution
V-Sync: off
Every quality option: off or turned all the way down

Singleplayer (infantry showcase):
GPU utilization %99(I'm GPU capped as always)
CPU utilization %25
Average FPS: 50

Multiplayer (40 player TDM):
GPU utilization: %43
CPU utilization: %23
Average FPS: 15

As you can see, it's a considerable FPS drop. My mate with a pretty beefy gaming PC also reports "his FPS is halved" sometimes. Though, on some 64 players servers I'm getting better FPS (~30).

In singleplayer I don't have any problem with the utilization, which brings me to the point: does the server performance influence client performance? If the server can't handle 40 players fighting in a small area, does it affect client performance too?

I'd appreciate if you looked into this issue.