using an auto cast for enh shaman is bad, because even if you do the /stopcasting you reset their swing timer. White hit dps is fair amount of shaman total dps and I think it is a bad idea to try and macro. I wish it worked like paladins where you can't spend it until you have 3 holy power. Honestly though, why would you want to automate it? Sometimes you need to save it for chain heal when you are getting low or 5 times healing rain. It's just not a good idea to automate it when enh shaman thrive on their versatility.