I'll see if I can dig up mine tonight after work. I went through this headache for a long time until I finally made a spreadsheet to understand it. I changed my chain heal macros to do the same type of effect as well, as what I found was once more than one of my shammys died, the macros was walking the list, and I would have 3 of them chainhealing the same target, rather each one targeting a different one.

In addition to a correct macro that works, I set up my rez on a round robin keypress so that it first does:

/assist Zappyzap
/cast [target=targettarget,exists,dead] Ancestral Spirit

That way if I'm running in a raid, and am helping rez people, i can rez multiple targets at the same time without much headache.