Ivory Cloud Serpent: Takes too long to spawn

I have been trying to farm this mount but it takes over 4 hours to spawn, at least. I have been trying for three days this assault (the Mogu Assault) and after four hours I simply must get up and do other things. (Like go to the restroom.) One to two hours is bad enough, but four and a half hours is simply unreasonable. I wish the developers would look into this.