Problem in Visio 2003 SP3 when saving a document as SVG
Arrow heads disappear for two reasons:
a) marker-end:url(#); bad links for marker type references are generated occasionally

b) style="overflow:visible;" missing, leading to cropped arrow heads on e.g. Batik
b) is easily patched by replacing
orient="auto" with
orient="auto" style="overflow:visible;"a) is harder since it is not obvious which marker type was intended