Lag in large scale battles

This is true on Guild Wars 2 such as in large WvW fights and just recently on Planetside 2.

When ever I go into large warfights with a lot of other players, my fps goes to 20..


None of my GPU or CPU utilization is maxed out; my CPU is at ~50%, GPUs at ~35%
Have updated video drivers, and chipset.

Especially on GW2 whenever I turn around in a large town or something, everything drops; my cpu, gpu(usage) and my fps goes to 5 for a very short period.


Specs:
W 7 64bit Pro
Asus M4N98TD - EVO
AMD Phenom II X4 955 (3.2 ghz)
8 GB Gskill RAM @ 1600
2x MSI GTX 460s
Corsair 850W PSU


Any ideas?