Since we got this out of the way, I can continue with the actual point.
I don't know how many of you are experiencing this, but I have had this problem with my past 3 computers.
Specs:
The Clan weapons shoot incredibly fast and if you pack 4 of them, it gets worse. Today I faced a 4x CUAC10 Direwolf. These fast shooting weapons produce a GIANT amount of explosions on your screen and we all know how well particles are handled in MWO.
Even with particles turned down to the lowest setting on an absolute top of the line PC, the game gets so laggy, I can't even react to the incoming fire.
And before you can even do anything, you're dead. Not to mention CW, where the baseline FPS are 30% lower anyways, even worse in lategame.
So if you want this to be a "Thinking mans shooter", make it a good shooter by fixing the core shooter-gameplay.