Game Mechanics: Named Skeletal Mobs depoping in Dalnir

[Dalendor]

Not sure if this is a green specific bug, or something more widespread, but we had two named Skeletal mobs depop after they "forgot" about our pulling them when they were AOE mezzed by an enchanter. The first mob was the Undead Blacksmith and the second was the Undead Crusader both from the third floor of Crypts of Dalnir. Our group was level 36-37 at the times of the pulls and depops. We have not seen the issue before tonight, we have only ever seen pets who lost their masters depop like this.
We pulled the Undead Crusader later and hit him instantly after the AoE mez and he did not depop. He did not respawn again during our play window for us to do additional testing.