More standard loot...especially at low levels you seem to get mainly money and mastery xp...and the occasional health crate or +% potion.
Gildings do not seem to be common in the blue boxes (or low level chars can not get them at all ) ...had around 12 boxes now always blue box had around:
35000 to 135000 mastery xp
money
and randomly potions, imperial insignia and atlantean shards
So, if the purple box has not at least ALWAYS 1 gilding token in it, it will not be worth the work at all. Might be a good idea to make these drop even in the green boxes with very low chance. As already said, do not make this content work for people with more than a handful of chars. Or make parts of the drops (or the boxes!) accountwide claims.
where is a vendor or exchange npc for the atlantean shards? What can be bought with them?