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 every Apprentice of Verata will raise Bone Fiends instead of their fallen and place great stress on the healers.
These Sages basically act as a distraction. They slow the warriors and take some time to take down, but they do not actually pose much of a threat to a party's health or spellcasting.