Considering these Augmented Weapons are Unique's, we won't be getting them every drop, so I don't think they need to add a lot of things to them.
I consider them to be an added bonus, something useful that is a little bit better than the normal Unique.
Another thought on the AU's. They appear to be learning milestone weapons. After you have fulfilled it's quest, the weapon unlocks, and also, you have just fought 20 spiders, meaning you now have more knowledge on how to fight that monster. As for the Gearhead axe, after fighting 1000 monsters, I would hope you have learned something about fighting many types of monsters.
Unless they are planning on you using these Augmented Unique's throughout your whole play up to level 50, you will find something better as you progress through the game, so at some point they will be less useful. So added another quest afterwards means that you might miss out on other interesting weapons, and I for one want to find and use the next Sword of Adam in this game