I'm starting to doubt just how well CPU optimized this game is. I the in-game benchmark on my brother's PC (I don't have the game myself). His system is a stock Core 2 Quad Q6600, Radeon HD 5770 1 GB @ 890/1300 MHz, 4 GB of 667 MHZ DDR2 RAM, running at 1440x900 resolution. The game was set to a mixture of performance and quality settings, I won't go too deep into detail on that. The point is, I thought the game was severely CPU limited, because even with everything turned to max performance (and unit size set to low), the in-game benchmark never returned a frame rate higher than around 20. So I bumped up the graphics settings as long as they didn't cause the framerate to drop further.
I just ran the benchmark with Afterburner monitoring in the background, and Afterburner indicated that the CPU cores were being underutilized. All four were active, but they were each fluctuating around 60% usage. Meanwhile the GPU was humming along at about 95% usage. This is unlike Dragon Age Inquisition, where each CPU core was kept at 90% usage or greater. As for other monitors, VRAM usage was around 800-900 MB (I tuned the settings so they wouldn't trigger the game's automatic downgrading to fit VRAM), and system RAM was at around 3-2.5 GB total use. There's just a load of untapped CPU performance in Total War Attila, just sitting there.
DirectX 12 can't get here fast enough.