Chain Harvest is so much better for raid progression and key pushing. Primordial Wave maybe looks good to whoever put it in our talents because of the colour theme but it is so bad and most of the time useless. Just paint Chain Harvest blue, and put it instead of PW. The base cooldown should be 2 min and then the first two talent points can reduce it by 15/30 seconds while the last talent can make it apply Riptide to its targets.
This is a very obvious and needed change for any Resto Shaman who knows what they are doing and I have no clue why it has not been implemented yet.