I ended up using a RotateTransform
on the chartarea for now to achieve what I was looking for...
I think that using the SeriesDefinitions as an abstract class is limiting towards allowing the developer to use chart-specific properties easily (i.e. PieCharts should have something like pies should start drawing on x,y coordinate).
| <RotateTransform Angle="-90" CenterX="50" CenterY="50"/>