This heroic Naigtal affix links mobs together so if you pull one mob a few more will come. At least that’s how it works for non-stealth classes. The affix also makes mobs share stealth detection, without showing an eye over their head, and expands detection range to like 50 yards. You pull mobs through walls from half the map away.
I’ve seen a bunch of conspiracy theories that some Blizzard dev got ganked too many times by a rogue and now has a vendetta against the class. But this affix looks like proof that someone is very specifically targeting rogues and trying to make them non-viable in new content.
Druids can always go tank and faceroll the mobs, hunters have tank pets. Only rogues have no tools to deal with this affix. WHY?!