I'm looking at the WoW book on how to play a Resto Shaman, and it basically says play a World Tree Barbarian. While this provides a strong buff in the way of single-target Temp HP, it provides no other healing. I've got some ideas, but I'm still working them out. For starters...
Replace Vitality of the Tree with Living Waters.

Level 3: Living Waters
Healing Rush: Providing healing or temporary hit points extends you Rage by one turn.
Healing Wave: Once per turn, while your Rage is active, you may use the Magic action to heal a creature within 30 feet. To determine the amount of healing, roll a number of d6s equal to your Rage Damage bonus, and add them together along with your Wisdom Modifier.

This seems to balance by requiring an action, but giving a 30' range and converting THP to healing. I'm still working on how to incorporate Chain Heal and Healing Rain for the higher level features. I'm thinking about expending a use of Rage as a Magic action, but still working on when and how to avoid making them OP.

EDITS for additional features...

Level 6: Chain Heal
Chain Heal: Expend 1 use of Rage as a Magic action to create a stream of living water that Heal the friendly target, then jumps up to 20 feet to heal the next 2 most injured nearby allies. Healing is reduced by 1/3 of the original target with each jump. To determine the initial heal, roll d6s for each Rage Damage dice, add them together and add your WIS modifier.

Level 10: Ancestral Toughness
Ancestral Toughness: When applying Healing Wave, you may choose to grant your target Ancestral Toughness, giving them an AC bonus equal to your Rage Damage bonus. Only one target may have this bonus at any given time and the effect ends when your rage ends. You may do this a number of times per Short Rest equal to you uses of Rage.

Level 14: Healing Rain
Healing Rain: While raging, the Shaman may expend 1 use of Rage as a Magic action to create an immoveable 10-foot radius cylinder of living rain within 30 feet of the Shaman. Allies standing in the area gain temporary hit points equal to a number of d4s equal to the Shaman's Rage Damage at the start of their turn, lasting for one turn. The rain continues while the Shaman maintains rage.

Any thoughts on the edits?

Healing Wave seems rather broken. Rage lasts for up to 10 minutes, so at 3rd level, you could restore about 850 hit points to the entire party.

Not being able to provide unlimited healing is a core principle of D&D; any healing should require expending a resource, not just an action. That resource could be a rage, however.

My thought was that straight healing is slightly less beneficial than THP, since THP can be given ahead of damage and prevents overhealing. It does add the WIS modifier, but other than that provides the same amount of HP as Vitality of the Tree. The main difference is making it use an action and giving it more range.

I thought I added this to my original reply, but...
Vitality of the World Tree at 3rd level, as written, is essentially like casting Power Word: Shield on the Fighter for 30% of his HP, every turn, for free. That is a bit OP at low levels, but that's what my Healing Rain was based on. It doesn't scale as well, being about 15% at level 20.

Quote from Elioron >>

My thought was that straight healing is slightly less beneficial than THP, since THP can be given ahead of damage and prevents overhealing. It does add the WIS modifier, but other than that provides the same amount of HP as Vitality of the Tree. The main difference is making it use an action and giving it more range.

The problem is you can use it outside of combat to provide a full heal to the entire party.

Quote from Pantagruel666 >>

The problem is you can use it outside of combat to provide a full heal to the entire party.

 Yeah - I didn't think about Rage being used out of combat. That needs to be addressed. Maintaining Rage when there are no adversaries should be made incredibly difficult. For this purpose, no rage means no heals.

Quote from Elioron >>

 Yeah - I didn't think about Rage being used out of combat. That needs to be addressed. Maintaining Rage when there are no adversaries should be made incredibly difficult. For this purpose, no rage means no heals.

It's deliberately made possible to allow using rage to substitute strength for certain noncombat skills (which is itself a kind of weird decision, but..). You could make the heal effect immediately end your rage.

They also want it to be able to stretch between a couple encounters in close sequence, vs only lasting for a single fight.

I noticed that the Healing Wave feature is limited to once per turn, which is really odd since most characters only get one action and the only features I can think of (Haste and Action Surge) both don't let you take the Magic action. I think you can safely omit that limiter.

I do also have a couple of thoughts about the new things you added.

Chain Heal seems a bit complicated and mathy (yes I know this is the math rock game). 1/3 is a very awkward number. Maybe the number of dice could drop by one for each heal?

Ancestral Toughness has so many uses available that, coupled with its anti-stacking rules and duration, I'm not sure it needs to be limited.

It's deliberately made possible to allow using rage to substitute strength for certain noncombat skills (which is itself a kind of weird decision, but..). You could make the heal effect immediately end your rage.

The kicker is that Shamans don't get Primal Knowledge - that feature is swapped for Totems.

Making healing end rage would make it more pointless than equating Path of the World Tree with Resto Shamans to begin with.

Quote from Elioron >>

Making healing end rage would make it more pointless than equating Path of the World Tree with Resto Shamans to begin with.

Nah, it would let you use your rage for the duration of the combat and then apply healing at the end. It's an entirely useful effect. Not being a WoW player, I don't know exactly what a restoration shaman does, but D&D healing is considerably more limited than MMO healing.

Quote from Pantagruel666 >>

Quote from Elioron >>

Making healing end rage would make it more pointless than equating Path of the World Tree with Resto Shamans to begin with.

Nah, it would let you use your rage for the duration of the combat and then apply healing at the end. It's an entirely useful effect. Not being a WoW player, I don't know exactly what a restoration shaman does, but D&D healing is considerably more limited than MMO healing.

 Yes! I was thinking about ending when you can't see any more enemies, but that isn't cut and dry either. Restoration Shamans are healers, most well known for water-based healing spells. All Shamans get their power from the elements: Earth, Fire, Water, and Air. I thought it was weird to make them Barbarians because, of the three specializations/subclasses, only Enhancement uses melee attacks as part of their normal play. Elemental Shamans are ranged casters, and Restoration are ranged healers. I've grown to appreciate the idea of their Rage coming from the power of the Elements flowing through them.

Trying to make it exactly the same is an impossible task. I think the intention was to provide an opportunity to have a WoW flavor within the D&D framework. The Enhancement and Elemental conversions seem pretty true to concept (though Elemental still doesn't use an actual action, just bonus actions!). I like the flavor of a lot of the other classes as well.

They really just phoned it in for Resto Shaman.  There's literally nothing that resembles the WoW spec.  Very disappointing.

Not crazy about the way they did Elemental or Enhance either, but at least if you squint you can kinda see some similarities.

I realize you can solve the out of combat healing by just making heal use a bonus action, because that means you can't use your bonus action to extend your rage. That does let you use it every round in combat, because you can extend your rage by using your action to attack or grapple, but if you use it out of combat your rage will end.

Just looking at the balance between healing specs, it's really absurd.

Druids get several useful healing and damage reduction abilities from Circle of the Land, access to the full suite of standard healing spells, and big WoW-specific c/d's in Tranquility and Tree of Life.

Evokers have access to lots of shielding and defensive utility from Sorceror, and five powerful, always-prepared WoW-specific healing spells.

Monks get five healing abilities from the Warrior of Mercy subclass, and a useful feat.  Mistweavers don't look as strong as the others, but they accumulate a lot of Focus points (which can be used to heal) and focus regeneration as they level.

Paladins and Priests get bespoke healing specs on top of a class that already starts with a lot of healing.  Resto shamans (whose base Barbarian class starts with no healing at all) needed a custom healing subclass too, but they used up the quota on Enhance and Elemental...

Quote from Belechannas >>

They really just phoned it in for Resto Shaman.  There's literally nothing that resembles the WoW spec.  Very disappointing.

Not crazy about the way they did Elemental or Enhance either, but at least if you squint you can kinda see some similarities.

 

 While I like the WoW supplement quite a bit based on initial impressions I agree that Restoration and to a lesser extent Elemental Shaman are not good at hitting the right feel. Champions of Azeroth (a large and mature fan-based project to bring WoW into DnD) is already proposing Druid-based versions of the Shaman and I am sure many others will crop up. 

This is what I went with...

 Shaman are spiritual adepts who commune with the elemental forces of the world and channel their power. These elemental forces are chaotic and, left to their own devices, would rage against each other in unending primal fury. A shaman’s call is to bring balance to this chaos, acting as a moderator among air, earth, fire, and water. A shaman’s magic focuses the elements to support the shaman’s allies or punish those who threaten them.

Shaman who specialize in restoration find a serene affinity for the restorative properties of water. They feel a profound spiritual connection with the source from which all mortal life takes root, and they wield that power to restore vitality to their allies. These shaman balance this healing focus with a command of the other elements, finding harmony in nature and purifying their allies as a tidal surge washes across a sandy shore.

Level 3: Living Waters

Your Rage taps into the life force of the elements. You gain the following benefits.

Healing Surge. When you take an action that grants healing or temporary hit points to another creature, your rage is extended by one turn.
Healing Wave. While your Rage is active and you are in combat, you may use the Magic action to heal a creature within 30 feet. To determine the amount of healing, roll a number of d6s equal to your Rage Damage bonus, and add them together along with your Wisdom Modifier.

Level 6: Chain Heal

Expend 1 use of Rage as a Magic action to create a stream of living water that Heal the friendly target, then jumps up to 20 feet to heal the next 2 most injured nearby allies. Healing is reduced by 1/3 of the original target with each jump. To determine the initial heal, roll d6s for each Rage Damage dice, add them together and add your WIS modifier.

Level 10: Ancestral Toughness

When applying Healing Wave, you may choose to grant your target Ancestral Toughness, giving them an AC bonus equal to your Rage Damage bonus. Only one target may have this bonus at any given time and the effect ends when your rage ends. You may do this a number of times per Short Rest equal to you uses of Rage.

Level 14: Healing Rain

While raging, the Shaman may expend 1 use of Rage as a Magic action to create an immoveable 10-foot radius cylinder of living rain within 30 feet of the Shaman. Allies standing in the area when it is cast, start their turn in the area, or pass through the area gain temporary hit points equal to a number of d4s equal to the Shaman's Rage Damage, lasting until the beginning of their next turn. The rain continues while the Shaman maintains rage.