Not sure if this is a bug or not, but the exotic champion bags, Branded Strongbox, in Thunderhead Keep seems to reward less than any other champ bag in the game. These bags don't offer any sort of gear or unidentified gear.
My suggestion would be to either update the champ bag to be in-line with other champ bags or replace them with the champ bag, Branded Geodermites. Those seem to properly give pieces of unidentified gear.
Edit: As of 5/15, the new map does drop a couple of Branded Strongboxes. They still do not give any sort of gear as a guaranteed drop.