The priority will usually be:
Intellect > Spirit > Mastery > Haste > Critical Strike >= Multistrike > Versatility
This is the primary of resto shaman stats. We get 1 spell power for every point of intellect we have. Not much we can do about this stat other than getting higher item level.
This is our regeneration stat, and you will roughly get 2.0625 MP5 (mana per 5 seconds) per point of spirit that you have. This is our most important stat, since getting more spirit will allow for more casts of expensive spells (looking at you Chain Heal). Spirit can only be found on necks, cloaks, rings and trinkets (in Warlords of Draenor that is).
The lower someone’s hp drops, the more healing our spells do. If the raid drops low enough, shamans are known to enter ‘god mode’. Once you have successfully achieved this state of shamanism, you are not likely to reroll anymore.
This amazing stat will scale greatly during progress. Mostly because people tend to drop lower at the start of progression (learning boss mechanics), and because of having lower health pools (lower gear). But when leaving progress and entering farm, this stat will become increasingly weaker. People get better at dodging mechanics and absorbs get so strong that you won’t drop low to begin with. Addtionally, health pools increase.
Increasing the amount of healers, will automatically diminish the healing a shaman is eligible to do. Simply because of how our mastery works. Discipline priests are your greatest enemy, since they prevent people from dropping low in the first place with their shields.
This stat will reduce the time it takes for us to cast our spells. Additionally, it will increase the amount of ticks we get from one cast of Riptide, Healing Rain, Healing Stream Totem and Healing Tide Totem. Don’t worry about haste caps because they no longer exist as they used to, blurred lines, partial ticks and all that.
This stat will increase the chances of earning a critical heal, hitting for 200%, and earning one of these will result in a return in mana for some spells by Resurgence. This is the reason why shamans are known to drop their spirit in (mostly at the end of expansions) in favor of crit. This expansion is different in that regard, since Resurgence does not seem to have the same effectiveness as it used to have.
Will increase our chances of landing a multistrike. You have two chances, equal to your multistrike chance, to earn an additional hit for 30% of the original heal. Multistrikes do not proc Resurgence. Has synergy with the resto shaman through our strength of stacked healing, which is where multistrikes proc abundantly. This has caused a lot of shamans to have warm feelings for the multistrike trinket from Blast Furnace in Blackrock Foundry.
This stat will increase your healing and reduce the damage that you take.