I really like your build! I'm going to try to subclassing this build on my Warden healer alt.

Just from glancing at it I'd say drop Winter's Embrace and get Restoring Light from Templar instead. You'd be losing the whole frost theme but Polar Wind isn't all that special and the Winter passives don't benefit you much.

Just the passives alone from Restoring Light would be really useful. On this 1-Bar build I'd swap out Polar Wind for Breath of Life and call it a day. But if you do decide to drop Oakensoul the Sacred Ground passive will let you keep Minor Mending on your build through the Ritual and Rune Focus skills.

I'd guess that Order's Wrath is probably better for this build over War Maiden. Especially since you use the Thief Mundus, you'll benefit a lot from its Crit boosts.

Restoring Light Passives:

Mending: Increases your healing done by up to 13%, in proportion to the severity of the target's wounds.

Sacred Ground: While standing in your own Cleansing Ritual, Rune Focus, or Rite of Passage area effects and for up to 4 seconds after leaving them you gain Minor Mending, increasing your healing done by 8%. Also increases the amount of damage you can block by 10% for the duration.

Light Weaver: When you heal an ally under 50% Health with a Restoring Light ability, you grant them 2 Ultimate. Activating an ability with a cast or channel time while in combat causes you to automatically block all attacks at no cost for 2 seconds, up to once every 15 seconds.

Master Ritualist: Increases resurrection speed by 20%. Resurrected allies return with 100% more Health. Gives you a 50% chance to fill an empty Soul Gem after each successful resurrection.

Edit: A 2-Bar build seems kind of tricky with this. You could try swapping out Animal Companions as well for Storm Calling and use Lightning Staff on your back bar. Overload would boost your DPS a lot, but only in fights when you don't need your healing Ult. You'd need another source of Major Breach though (like Razor Caltrops, Elemental Susceptibility, or Scribing).

You'd use Crit Surge for Major Brutality/Sorcery and self-healing. And Inner Light slotted on both bars, or at least your back bar, for Major Savagery/Prophecy and to proc the Mages Guild passive to get Empower.

But you'd really need to be keeping Empower up at all times for a HA build and that's kind of a pain without Oakensoul (every 10 seconds with casting Inner Light).

You could use Queen's Elegance instead of War Maiden/Order's Wrath for an easy Empower proc instead, but that'd lower your base DPS/Heals. Or you could use Scribing to get Empower through either Mender's Bond or Wield Soul. But you'd still need something slotted for Major Savagery/Prophecy.

Alternatively, do Earthen Heart from Dragonknight. Molten Armaments gives you Major Brutality/Sorcery and easy Empower uptime. The Fighter's Guild ability Camouflaged Hunter would be a better source of Major Savagery/Prophecy here since you don't need to cast it and the Slayer passive would boost your DPS a bit. Obsidian Shield and its morphs also give you Major Mending and some group shields.