Actually, loading dependent views is done with a simple region behavior and a custom attribute. This is all it take me to accomplish this task. I simply attribute my view with all the views that must be loaded into their respective regions. Then when this view is navigated to, all the dependent views are also injected into their regions. Oh, and if they implement a certain interface, they will also share the same data context (ViewModel).
[DependentView(typeof(ViewBTab), "RibbonTabRegion")]
[DependentView(typeof(ViewA), "SubRegion")]
[DependentView(typeof(ViewC), "SubRegion2")]
public partial class ViewB : UserControl, ISupportDataContext
{ ... }