Ok so I'm going to be as thorough as possible...

Usually I'm good at this but this one got me stumped!

Intel i5 2500k @ 4.2Ghz (H80 cooled)
XFX HD 6970 CF
Maximus V Formula
16GB Ripjaws Z 2133 (1950Ghz)
1000w Fatal1ty PSU

So this is the weird part. On Very High, everything except Objects, which gives me horrible tear, I run the game perfectly fine. Solid fps no lag nothing. Smooth as butter. BUT, while I'm playing on multiplayer, the second an enemy is on screen I get a lag spike. Usually lasts less than a second. If there are no enemies on screen I can run around shoot, throw, jump etc. without having fps plummet drastically. The weirdest part is that its only when I get an enemy on screen... Yeah yeah, I know. I svck, maybe its not the game maybe its you. I agree, I do svck! But its definitely not my playing skills lol

What Ive done:
flushed dns
restarted/rebooted router
antivirus/firewalls check out fine
safe mode
very high settings, medium, low settings with CF on and off
CF enabled, CF disabled
AA OFF
16x
checked cooling, temps are reasonable nothing passing 70 on cards and cpu barely hitting 60
drivers up to date, ccc up to date. NOT using the beta drivers
tried different servers

-I did a little more runs and recorded with fraps gonna edit and see if I caught any while recording. Noticed its not just when I see enemies >_>

Hopefully other people have had this problem and can help me out! If you guys need anymore info let me know. thanks!

use msi afterburner to check your memory and gpu usage when these fps drops occur

It is normal on MP .Lower your settings to low that should help you.