Iceciro
Special Ability: Decimate
Something about the defense promos makes the AI not consider running them as much as it really needs to 


I've had barb units of all kinds pillage my improvements, including an axeman or two...
On the other hand, I love the promotions system, but I never bothered making my workers defensive: they will die anyway if they are attacked. The AI gets too often that +1 defense, which makes it even worse at building improvements. That hardy promotion should be increased to +2: workers as strong as scouts... but they cost three times more than a scout and can't attack, so it's not like you will depend on them for defense. The second and third hardy promo would be unlocked with later techs (bronze working and iron working? In the sense that workers have better tools and they can use them to defend better...). Still, even +2 wouldn't compete to faster working rate, imo. The AI just doesn't realize that.
Then nothing can ever attack them (though anything can share their tile and pillage whatever they just finished)