Personally I go for a fairly focused blood-hunting strategy most of the time (5 provinces with 3 B3+1 hunters in each), but I would have to agree that with mainly fodder as patrols the 3 High Priests would be hard pressed to stop a Van raiding party. But due to having B3 it might not be impossible (no manual here, due to this I don't know if there are some decent spells vs. Van in B1-3).
Guarding 5 provinces with enough units to repel a raid in addition to having some armies claiming Van provinces and hunting for its home province might be too much even with the cheap troops.
But this depends on the phase of the game and how it is progressing overall. The roughly 120 slaves I get this way while "wasting" 90RPs might not be that attractive all the time
But I will take a look at this in the testgame, too (EA).
CharonJr