Don't know if this will help, but I get "waves" of what you describe - usually after a couple days, but not always.
Reboot,
Unplug/repower your router (or whatever, if you have),
Kill all non-essential user processes (i.e. "clean" running environment - I had a photo toolkit background process that hated Crysis),
if your anti-virus doesn't support "gamer mode", you may need to shut off while playing (I do it either way, but no material effect on my box)
Delete shaders
Play....
lol.. that's the alchemy that let's me play a day or two on my older PC.
Once I start getting the "stuttering" during just a couple people around me, or start having trouble/crashes w/ MWLL models, I have to do thd above.
Yes, I know it's a little silly, but it seems to work - or at least maybe it will help you pinpoint problem area.