we just did the event in tomb of valor with a group between lvl 28 and 32, and lord chesguard did not drop anything. in the past he used to drop at least an adept.
that mob is for a quest, most quest mobs don't drop loot. Any mob in the game can randomly have a chance to drop loot, maybe when you got that adept from him last time you did him it was just a random luck drop.