Dastana were intended to help boost a light armor wearer's flat-footed AC without giving them too much - they're essentially bucklers that you can only wear with padded, leather, and chain shirt armor, and you can wear a buckler at the same too. that's not really that much - +6 total (with the chain shirt). At low-levels, anyways.
Most DM's that I've played with allowed dastana, but there wouldn't be stray dastana sitting around in a pile of loot, I'd have to spend my scout's money on buying a pair of masterworks, 'cause I frowned on the armor check penalty, then on getting them enhanced later on.