hmmmm.... I thought you would have made them more middle-eastern-ish with their appearance and names National Geographic provides good source material for both you should have included a battlefield imam in their party
Well Tallarns were actualy a forest/plains people, then chaos marines V-bombed there planet leaving no life with the exeption of the people in shelterbunkers. So they 'only' have 10.000 years of experiance. And maybe leaving the water of the dead with the dead is a funaral tradition like putting coins on a dead persons eyes.