Ah, good question, Nick!
The issue is that if there are N wires, then there are N arrowheads -- and if they don't all line up exactly, it looks messy (and it's less efficient to draw). With the way the bezier curve tangents work, my implementation caused the arrowheads to be slightly off horizontal, but it looks like your implementation solves that issue... (hmm, maybe not, since I don't see multiple wires attached at different angles)
The advantage to putting an arrowhead on every wire is that each node does not have to know how many wires are attached, and since that information is stored on the source node (instead of the target), I can see why you would want to not change the shape of the node's port.
Either way, glad you are thinking of implementing arrowhead... one less piece of Editor customization I'll need to worry about in the future -- cheers!
