As already mentioned, the Vos (with elements from Slavic and Russian cultures heavily drawn in mostly, with very few elements from Scandinavian cultures) tend to find that there are earthly powers that can be conjured from within one’s body, a sort of latent power of magical properties; people confuse divination and magic with bookish people who would never fall in a rage, but this shows they lack an appreciation for the magical traditions of millenia of various cultures, including African animism and Slavic belief in daemons of the land and so on… In fact, I believe that any disciple of the ways of Vorynn, back when there were no blood powers and no human could employ true arcane magic - since none of them had a bloodline and the only mages they had were bards and magicians, would probably not consider it an error or a foul idea, becoming a barbarian (in the sense of taking levels in that class), opening up this path of his soul.
Bards would generally not be taken very well from Vos in modern times; they are simply tolerated, and probably ridiculed, but that’s that. Woe befall the fool of a bard who weaves an enchantment to enthrall his audience!
As for the Rjurik, I really would never see them as accepting raging as an honourable thing; true, some of them may be doing it, but I suspect they are thought of as dangerous madmen if not even cast out from their tribes at least.
Spellcraft is not meant to make the difference between arcane and divine magic; it’s a practice, a skill of how talented you are at using the finer aspects of magic, such as preparing a ritual or a binding circle of power, and how capable you are at taking notice of these aspects in the magic around you. Anyone can make an educated guess about the kind of magic employed by a person: priests generally do not shun armour, on the contrary they seem to wear it a lot more than other spellcasters (a categorization that seems artificial to the people of Birthright: to the bulk of the population of Cerilia, it fits the bill only when it comes to arcane magic), and they tend to wield lethal weapons, heavily emphasizing on some aspects (according to their patron/matron deity), wear holy symbols and, most of the time, some indication of their station in the priesthood; on the other hand, bards tend to wear light armour, wield swords, and prefer avoiding combat at all if possible, also being noted for vast knowledge over almost any topic regarding times past and important people and places, finally characteristic about their slightly roguish ways and their tendency to have a musical instrument at hand or sing (note, for example, that enchantments are woven by spellsongs); finally, magicians tend to be sprightly types carrying a lot of peculiar stuff and wielding a wide range of simple weapons, but generally shunning armour, also characteristic of their long absence every morning and tendency to use a peculiar, rolling language when casting a spell; wizards and sorcerers are vastly more obvious. Of course, this has a bit of a hyperbole, but that’s not the truth about magic: that’s just how people believe magic is about these people (and it generally is worse in their eyes).