As I mentioned at the end of this answer the IActiveViewEvents.AfterItemDraw event (even with IViewManager.VerboseEvents enabled) only seems to fire for layers in the root of ArcMap's table of contents, not nested sublayers, so if you want individual events to be fired for a layer it must be moved into the root of the TOC and not within a group layer.
Does anyone know of a workaround for this or have findings to the contrary?