It is difficult to take on these cultists with a party of henchmen or less than level 20 players. They can overwhelm a party and their patrols are closely tied together. Luring a few will bring about at least six cultists, and these necromancers will raise Bone Fiends instead of their fallen and place great stress on the healers.
One useful technique against them is to hit Verata's Apprentices hard. They will use Taste of Death and kill their own minions to save their lives. Another tactic could be to bring a necromancer in the party with a fast casting corpse exploitation spell. Verata's Aura can also be used to turn their own undead minions against them, but it is important to be careful of their Verata's Gaze.