Planetside 2 problem

You can't do anything about it.

complain about the optimization on the official forums

I'd say your problem is not your hardware, it's way better than mine and i can play fairly well (i'm pretty low on ram).

I'd check ATI for updated drivers, though it's well known PS2 doesn't like ATI cards much.

Though if you are in the middle of a massive battle, your FPS will go down no matter what. It's still something they have to address.