When defining a slanted wall with a base offset, Revit calculates the slant from the base without accounting for the base offset, which displaces the wall, making the tool unusable in many applications. My idea is this: Autodesk should fix the wall slant tool, so that it works properly and is useful to designers. It's great that you implemented a feature users were asking for. Now, we would ask that you make it work. Please, and thanks.