While good in theory, I'm inclined to say its probably not necessary and would just be apt to irritate people if it went off frequently. The only macro I used for healing is one that announces who I am raising just to make sure me and another healer don't grab the same person. I'm only part way into AST but as WHM I don't run into people dodging my heals too often. Now and then I'll notice a lone bard standing at the opposite end of the arena but usually if I move between him and the rest I can reach fine. For raids etc I could maybe see having one off to the side encouraging people to stack that isn't connected to your actual moves just in case you have a party who needs a bit more guidance but aside from that I can't think of much cause for it. If someone is dodging your heals that frequently, give 'em a scare and let their health dip. XD. Nothing will send someone running to a healer faster than the fear of death.