Constant ~100% CPU Usage with Variable GPU usage (Crossfire) Low FPS

First time posting after i cant find any solutions. Please go easy 🙂

Okay so here is my issue.

After buying a 144Hz monitor, I was aiming to hit 144 fps in BF4 in order to make the most of it. However, the CPU usage of the game seems to be fixed at 100% no matter what settings i choose, meanwhile, the GPU usage across both cards varies depending on the game settings. As the settings are lower, the GPU usage is lower, resulting in NO increase in fps. I find it hard to explain, but hopefull the screenshots should clarify the issue. 

This is causing me much frustration and would really appreciate some help on the issue 🙂

What ive tried so far:

1.  Updating to latest GPU drivers (Were already installed)
2.  Unpacking cores on my CPU (No idea if that even does anything)
3.  Re-installed the game to my SSD
4. Considered CPU as bottleneck, however after looking at various forums, this should not be the case. 

Screenshots for proof of issue:

(Note CPU/GPU Usage and current FPS)

NOTE - Game resolution is set to 1080p no V-sync etc.

1)

200% Render resolution and default Ultra Settings.
http://i.imgur.com/d7X62x8.jpg

2)
100% Render resolution and default Ultra settings
http://i.imgur.com/hsGoM3q.jpg

3)
100% Render resolution and default low settings 
http://i.imgur.com/LjLTZoK.jpg

4)
25% Render resolution and default low settings 
http://i.imgur.com/6u9ozRl.jpg

Rough system specs:
I5 4670k @ 4.2 GHz
Crossfire MSI r9 280x
8.00GB Dual-Channel DDR3 @ 800MHz (9-9-9-24)
512GB SSD
850W Corsair CM PSU

Windows 7

Complete system specs can be found here:
NOTE - CPU is overclocked to 4.2Ghz
http://speccy.piriform.com/results/f7v2lGRCneclOHS6VUtddFm

Please please please help as i really have no idea what lest to try.