Light lvl 80 Exotic armor takes 11 Insignias to make.
Medium lvl 80 Exotic armor takes 8 Insignias to make.
Heavy lvl 80 Exotic armor takes 10 Insignias to make.
Box of Berserker’s Draconic Armor (Exotic) will instead give you Berserker’s Gladiator Armor (Rare).
I also believe that the lower level (sub 80) exotic sets require more insignias in bulk than they do individually.
Edit: On a side note, it would appear as though the Masterwork bulk sets (possibly rare/fine as well) require about 55-60% of the normal materials in order to craft. IE: 48 Potent Blood rather than 90.