Well at the beginning of the figth the firstTank takes the LK and the second one waits for the Shambling Horror to off tank him.
The little Guhls on the side of the MainTank get interessting in a second
Lets say the "Shambling Horror" spawns and the offtank takes it. Well usually the Caster tend to dps him down and switch back to the LK.... BUT
I dont know the english name "Nekrotischen Seuche" (15 sec -> 50k dmg )
If someone gets infected.. he runs to the OffTank and than gets decursed. Well this is normal, but now the clue. The Offtanks taunts an little Guhl... JUST ONE ... and also tanks him.
This means the Tank has the Shambling Horror and "1" little Guhl. Also the "Nekrotischen Seuche (15sec > 50k)" this jumps from Mob to Mob and adds up to an 500k BANG. If a little Guhl dies.. the OffTank taunts anotherone. We endup whit just 1 or 2 Guhls left and the Offtank kills the "Shambling Horror" by himself.
Keep bringing the "Nekrotischen Seuche" to the Offtank. This provides even higher Stacks.
Have Fun.