I'm on a binge of making builds starting with a mini or artwork for inspiration and working from there. These are being used as backup characters for players that die in Rappan Athuk.
So anyway, I'm doing this guy next.
Human Barbarian, 6th level, dual wields Falcatas, 20 pt buy.
Thinking Fighter dip Weapon Master or Ranger with TWF combat style and less Dex.
The fact that they are one-handed weapons, means you can two hand them for more damage on single attacks.
When you full-attack, you can fight with both, and still have them count as light weapons for the purposes of penalties.
This - but you will need Quickdraw to be able to pull it off right.
Well, I have to admit that I am not really that familiar with the Weapon Master Fighter so I can't comment on that. I've heard good things about the Mobile Fighter though!
If it was me I'd take Ranger to 6th at least. I'd pick up TWF and ITWF with bonus feats. I'd probably skip Double Slice at the moment. Fact is Weapon Specialization (which you will get from Fighter) is twice as good as double slice for a character with an 18 STR (it adds +2 to damage with ALL attacks, rather then just the off-hand ones).
At higher levels you'll probably have a DEX item that will let you take Double Slice with a Fighter feat - then you have the option to retrain it if you didn't find it gave you much mileage.
Going Ranger lets you focus on STR & CON. You're going to be giving and receiving a lot of full-attacks so being able to save points on DEX is nice.
After that I'd probably go Fighter 10? Maybe more? You could go 10/10 and pick up GTWF as well as "Instant Enemy" I believe...