Yes. You can have (Light) Armor, Shield, and Dastana... and Enhancement Bonuses on all three... The penalties are, weight for all three, and Enhancement Bonus costs on all three. Since Dastana can only be used with Light Armor (the three listed, plus, I believe, Studded Leather, unless I remember incorrectly), it isn't really a big deal.
Treating Dastana as a Shield doesn't work, IMHO. Shields require a proficiency that Rogues don't have, and can also give a +2 bonus, whereas Datana give only +1. In other words, shields are better.
Only Rangers, Rogues, low-level Monks with no WIS Bonus, and Wizards or Sorcerors will be interested in these devices, anyway. Maybe Bards. To require shield proficiency to use them (as a mere +1) pretty much removes their reason for being...
Bracers of Armor become more interesting, though... Aren't Bracers just Dastana? ;-)