Simple: If I haven't changed the definition of the entity, don't re-validate that entity when updating other entities in the model. Current state, if I have a dataflow with multiple entities (they almost always do) each entity must be refreshed numerous times simply to alter/create any other entity. This is wasteful and time consuming behavior.
Additionally - provide a UI option to selectively, and completely, bypass validation (per entity.) It would increase the efficiency of this feature enormously.