The Druhzniks have the same helmet many of the Vaegir Lords did in Warband. I don't really see what's wrong with that. I personally don't like the helmets myself, but they don't really bother me. Can easily equip a different helmet, and use different Cavalry. Since a Nordic inspired army wouldn't have many riders to begin with.
Also, Kievan Rus, are literally Russian Vikings. While the Norse, Danes went to England and France, the Swedes and Finnish went to Russia. Novgorad and Kiev are both Viking Settlements initially that Russia ended up taking over and integrating. So for them to have heavy Viking influence makes sense, whilst mixing it with more Slavic cultures as Russian culture took over.