Some of the feedback that was provided were accurate, while other things weren't bugs, and finally some we're still researching evidence for. If you would like to help us out, please investigate whether the behavior below is blizzlike or not:
- Plagued Ghoul is Immune to Shackle Undead
- Plagued Deathhound is Immune to Stun
Pretty sure the Ghouls are indeed supposed to be immune to shackle. I can't recall having seen them shackled back in the days, it would also make it too easy.
As for sources, unsurprisingly there's not much info about those trashpacks out there, but Wowwiki states this: 'Tank them away from the group and kill them last. They are stunnable, so stunning is a good option to reduce damage and cleaves.' -
http://wowwiki.wikia.com/wiki/Plagued_Ghoul?oldid=407607
It says they are stunnable and they have to be tanked apart -> kinda indicates you couldn't shackle them otherwise it might have been mentioned as an easier tactic.
For the Infectious Ghouls (Ghouls in the Plague Wing, before Noth) it is mentioned that THOSE are SHACKABLE, but those Infectious Ghouls are different from the Plagued Ghouls that are placed in the Outter Ring of Naxxramas.
Infectious Ghouls: 'Vulnerable to stuns, slowing effects and
Shackle Undead. Kill them one at a time.'
-http://wowwiki.wikia.com/wiki/Infectious_Ghoul?oldid=406863
That should hopefully prove enough that the Plagued Ghouls should be immune to shackle. cause otherwise it should have been mentioned on the wiki. But again, it's indeed more indication than solid evidence.
Couldn't find anything about the Deathhounds, but those have bare been killed at all back in the day, cause you usually never crossed their paths on the way to the wing end bosses.