Landslide stunned me then summoned 4x Theradrim Shardling but they didn't attack me because I was out of their pull range, Landslide chased me and I killed him but the adds didn't disappear.
Quote
By Slange (13,944 – 2·22·108) on 2008/05/04 (Patch 2.4.1)
All his spawned shardlings will despawn when Landslide dies, so if you have a way of tanking those don't bother killing them and just focus on Landslide himself.
Alucard-entropius
commented
4 years ago 
Landslide stunned me then summoned 4x Theradrim Shardling but they didn't attack me because I was out of their pull range, Landslide chased me and I killed him but the adds didn't disappear.
https://classic.wowhead.com/npc=12203/landslide#abilities