Tested and Working.
I was doing Mount Hyjal with my guild yesteday and wiped on Archimonde. As soon as I released, a pop up window apperead asking me if I wanted to ressurect. I cliked accept. The next thing I knew, I was rezzed up at the grave yard with no sickness or anything. I found it kinda weird and thought that it was just a one time thing.
I tried to repeat it by adding some lag on my end and BAM, did it again. This could potentially save you lots of time from walking all the way to your corpse when you can get an instant rez at the GY and mount up, the trick is to lagging up a bit before you click the release button.