What is the trick to doing the primeval lich champ spawn?

[Demonous]

Ive done the spawn about 5 times now, 1st time i got 2 items that i could pick up, next 3 i got 1 item, and this past time i didn't get any items.... i don't see how people are putting together full racks and vats, etc at that rate so there has to be a trick to getting items

 

[JC the Builder]

They are doing the spawn a lot.