Revit Legends are completely unusable in their current state. Placing "Dumb" drafting components on a sheet that don't allow dimensioning, linework, tagging, or any editing whatsoever is contrary to everything BIM is trying to move towards.
In our office we create special phases, sections, elevations, and plans for all of our legend components. Thereby placing the actual 3D components into the views and having all the customization of a regular 3D component. Especially the ability to tag and propagate through the whole model any edits to the parameters of the specific element.
It works well enough, but that doesn't change the fact that it's one of the dumbest work-arounds to something that should be inherently intelligent and usable in Revit.