Necro + Cleric can kill it, the cleric will have to do some healing, if he mezzes the necro pet and your not superman fast with demezz of the pet, your cleric could die.
Attacks using weak physical attacks and casts rotating resist DDs. He can and will cast: Root, Mezz, Fire DD, Cold DD, Matter DD, Spirit DD. I have not seen disease or poison come up.
Caba ML9 pet with friar HoT can kill it also if it has cleric buffs.