Sauromantian Soothsayers: are they there exclusively to feed my evil blood rituals?

[Poopsi]

It seems to me that in general, Sauromantian soothsayers by themselves are fairly useless spellcasters. With one astral dot they cannot cast any of the nicer astral combat spells. They cannot even cast starfires, for chrissake. The one thing they can do is cast communion. On the other hand, we have Witch kings, which have access to blood magic. However, they are p¡ss poor at it out of the box, which means that the blood spells you can cast will cost an absurd ammount of fatigue, so you need a communion. Problem is, witch kings are expensive: it´s bad enough to have to pay 300 for an unit and have it sit around hunting blood slaves, if besides that you have to buy eight of them to be able to have one cast blood combat spells reliably, it´s a sorry deal. Specially considering that sabbaths, unlike communions, which cost just fatigue, need blood slaves to be fueled. So you´d need to spend six slaves just to set it up. Ok, blood slaves are cheap, but that´s just a waste, and if you are deep in enemy territory, replenishing your stock might be harder.
On the other hand, if you use soothsayers instead of witch kings, setting up the sabbath costs you only one blood slave, a much more reasonable price: if you bring with you 30 blood slaves, you´d not need to restock for around six turns, if you spent every battle one slave setting up the sabbath, and four in attack spells.
This is the only useful role I see for them, really. I do the same with midgardian volvas, but at least, with two astral dots, they can do more parallel things.

As a side note: is there some alternative to this in regards to blood magic? The spells are too expensive for them to be used without a communion, and sabbaths are too expensive to be worked reliably, imho..