"Pick Pocket loot table for a mob generally resets after about 10 minutes.
The Pick Pocket ability can also be resisted, which will remove the Rogue from Stealth. The chance for Pick Pocket to be resisted is based on the player’s level in relation to the mob’s level, so if the player is higher level then the resist chance will be lower.
It is also worth mentioning that not every humanoid mob will have a Pick Pocket loot table, and other mobs (demons, such as satyrs) may have a Pick Pocket loot table. The rule of thumb is that if the mob physically looks like they might have pockets, odds are they have a Pick Pocket loot table."
So my guess is that you’ll resist BRD mobs more because you’re not at least 10+ lvls higher than them.