[sriram_malhar]

I don't see why arrows must start at the middle of an edge. Sometimes multiple arrows from an edge look better if the end points are spaced apart (to emphasise the connectivity visually, for example). There are times when an arrow is positioned just on the inside of a corner, depending on what it is connected to and the angle of the arrow with respect to the edge.

In the final analysis, one should strive to get a visually balanced look, which takes into account placement, thickness of lines, density of information etc. There is no one-size fits all.