Yes Im sorry to say that the high heat of soap making does kill the benifits of the herbs.
Its also hard to scent soap with fresh herbs, the scent burns away. When using E/O's wait till the last poss min so its as cool as can be with still being able to stir in your E/O's, other wise they just burn away. I think milling your soap after you make it is the only way to keep in the benefits of the herbs.
Tea or oil should be fine as long as you sub the tea for the water in the recipe.
Im not a soap maker but I wanted you to have a reply with some kinda help. Cory Su cooks up wonderful cold press soap and shampoo. I think she has some stuff in the bazzar.
We have lots of soap makers here, hopefully someone can give more advise!