I can't say I'm really impressed with the performance on my rig either.
Intel I7 3770k water cooled and overclocked
16gb RAM (800 MHz dual channel)
EVGA GTX Titan (overclocked)
and Arma 3 installed on a 256gb Samsung 840pro SSD
I want to write a wall of text, but I'll just say that the engine needs a serious overhaul. That's what I wanted to see with Arma 3.