To kill Thorim easier you can mindcontroll 2 Mobs.
The first Mob is needed also for a achievement but also makes the fight much easier.
It gives everyone 20% HASTE!
Dark Rune Warbringer - NPC - World of Warcraft
The second Mob is "just" a healer.
But his heals are really heavy and are good to keep the tank alive.
He has a hot which ticks for 10k every 3 sec and direct heals for 50k
Dark Rune Acolyte - NPC - World of Warcraft
The Dark Rune Warbringer spawns in the Arena and the Dark Rune Acolyte is on the Way to Thorim.(Sheep the last acolyte before the second miniboss, jump down into the Arena. The Healer will come to the Raid through the door which is locked.)
greets Elite