Ridiculous lag!! Please help! :(

[XxRamboJuniorxX]

Ok, so basically I've been playing the Planetside 2 Beta for about 2 days, and I'm not sure if it's because of the lack of optimization or some other factors, but my frame-rate while playing the game is HORRIBLE during firefights.
I can have the settings on high, or custom (high-medium) anywhere in the game and it will run really smoothly, with about 40+ FPS; but as soon as I go into a firefight, it literally goes down below 10 FPS and I really don't understand what's causing the problem.

I've tried many things such as putting all of settings as low as they can be, reducing the Graphics Rendering tab, changing the resolution, and in the end I get the same end result despite all of my efforts (Ridiculous lag in firefights)

If this is an optimization issue and will be fixed eventually, please let me know because I really enjoy this game, but I can't help but not want to play it anymore when I constantly get killed because of lag, and how it doesn't look as smooth as it could. However, if it's a hardware issue; Please inform me of what I need to upgrade so that I can truly enjoy this masterpiece of a game :]

For other references: I can smoothly play Battlefield 3 on high settings with a resolution of 1680x1050

My Specs Are:
-OS: Windows 7, 64-Bit
-Processor: AMD Athlon II x4 640 3.0 GHz
-GPU: XFX Radeon HD 6770 1 GB GDDR5
-Memory: 5GB RAM