I camped him for 5 hours and got nothing, the robe looks very cool and is easy to get except for this part....i suggest coming with a few friends and hunting the entire zone, some named mobs are fun to kill for the drops and you can sell most items in bazaar for 500-3kpp depending on where you hunt, this is incentive for your friends and guildmembers to help you =) Happy Hunting
He pops at the NW camp, by the house closest to Katta. He spawns at the right side of the ramp up to the house, as you are facing it (or the left side if you're looking at it from the zone wall). That position can spawn either a PH, the Gladiator, or the named that drops BL tunic mark (forget the name). It took me 7 hours of constant killing to get him to spawn. Good luck.