Hi there! I'm interested in this topic too!
I see the arc-shape and the other shapes in Blend for Visual Studio 2013 if I open a Silvelight project, but if I open a Windows Phone 8.1 (not SL) project the only shapes are ellipse and rectangle.
Path is not the same at all because I can't easily change the path shape to reproduce the arc-shape parameter modification behaviour (for instance the start or end angle of an arc shape) at Runtime.
Is there an alternative way to draw some parametric shapes such as a curved progressbar or a simple pie graph?
Thanks!