Definitely a CPU bottleneck I'd say. BF3 64 player maps are really demanding on CPU power.
About the RAM issue, if you can run the RAM at 1333mhz with 3.8ghz then that would be fine, and you can drop the CAS to 8. At that point you might try incremental increases to the FSB, to maximize the speed at CAS 8. At 1.5V it might be stable up to 1400mhz or more.
Just to clarify, you want to drop the 9-9-9-27 to 8-8-8-24.
Here's an interesting read:http://forum.giga-byte.co.uk/index.php/topic,2515.0.html