So just by looking at what you casted on Skorpyron during the fight I just have a few suggestions that might help your HPS.
Cast Healing Rain as soon as it’s off c/d – The placement of this will really make a difference as well so you will need to place it most likely in melee or where ever you see the most ‘bodies’
Cast Healing Steam Totem every time it’s up – it looks like you only casted it 5 times in a 6 minute fight, should be a lot more.
When using Cloudburst – you really need to align it with incoming damage and have it explode at the right time; I personally only use cloudburst for select fights where I really know I can time it correctly for my heals to boost it and for it to explode and heal at the right time.
Gift of the Queen – should be used a lot more, this should be used on c/d as it doesn’t cost you any mana
Really a lot about a shaman is c/d management – just learning the fights and knowing when to use your big c/ds will also help your HPS alot.