In the Copperbell mines where these quest mobs are located, if I pull a mob near the bridge close to their spawn point an extra dapper cadaver mob will spawn. I have confirmed this is not just an extra aggroed mob I have lost track of. I have seen the mob actually spawn on several occasions.

This occurred on Karnak at 1:00am 11/6/2011. I was not in a party at the time.