From Using and checking the following builds:

https://alcasthq.com/eso-magicka-templar-healer-build-pve/
http://esoacademy.com/builds/the-elder-priest-healer/
http://deltiasgaming.com/eso-templar-pvp-healer/

And Mainly from this one:
https://alcasthq.com/eso-magicka-templar-healer-build-pve/#content4

Rotation:

I have come up with this build mainly focusing on Dungeon Healing. The rotation on heals that on the main bar are the following:

1 - Pop down Healing Spring on the tank (once they have brought the mods together) and keep popping this down when the tank / dpsers get to around 70%.
2 - Get as close as you can and pop down the Ritual of Retribution and only re-use this once the circle disappears.
3 - Then keep Rapid Regeneration active at all times. Great for those top-up heals. You basically keep an eye on your own timer so when it gets close, cast again.
4 - When fighting the boss, pop down a few Combat Pray when the health is looking around 50%. This gives the group some minor passives which help.
5 - If the situation is getting dicey (like having a dpser queue as a tank - the classic cloth tanks) then blast the first SOS of Breath of Life. Try not to spam too much as this is costly!
6 - If it gets worse and the ultimate is ready, pop down the SOSOS Light's Champion.

For the bits in between when everyone's health is looking good (90%+) then just use your retro staff as mods to do a gentle heal.

Vampire:

This bit is up to you but (From Deltias Gaming) the mobility provided by Mist Form is too good to pass up. The Undead passive remains one of the more “busted” overpowered in the game and we have a self cleanse. Are there downsides? Sure, Dawnbreakers, siege, Fire etc but the positives outweigh the negatives.

I keep Vampirism to Level 1 by Drinking a Double Bloody Mara.

Gear set (Before Trails):

THis is the following gear setup before doing the trails:

Monster Set:
Head (Heavy- Infused): Nightflame (Elden Hollow II) or Chokethorn (Elden Hollow I) - Glypth: Truly Superb Glyph of Magicka
Shoulders (Medium - Divine): Nightflame or Chokethorn - Obtained from Maj al-Ragath's chest - Glypth: Truly Superb Glyph of Magicka

Gear:
Chest (Light - Infused): Sanctuary (Banished Cells 1 or 2) or Kagrenac's Hope (Can Only craft this) - Glypth: Truly Superb Glyph of Health
Arms (Light - Divine): Sanctuary (Banished Cells 1 or 2) or Kagrenac's Hope (Can Only craft this) - Glypth: Truly Superb Glyph of Magicka
Leg (Light - Infused): Sanctuary (Banished Cells 1 or 2) or Kagrenac's Hope (Can Only craft this) - Glypth: Truly Superb Glyph of Magicka
Belt (Light - Divine): Sanctuary (Banished Cells 1 or 2) or Kagrenac's Hope (Can Only craft this) - Glypth: Truly Superb Glyph of Magicka
Feet (Light - Divine): Sanctuary (Banished Cells 1 or 2) or Kagrenac's Hope (Can Only craft this) - Glypth: Truly Superb Glyph of Magicka

Jewellery:
Necklace (Arcane): Sanctuary (Banished Cells 1 or 2) or Willpower (Imperial City) - Glypth: Truly Superb Glyph of Magicka Recovery
Rings (Arcane): Sanctuary (Banished Cells 1 or 2) or Willpower (Imperial City) - Glypth: Truly Superb Glyph of Magicka Recovery
Rings (Arcane): Sanctuary (Banished Cells 1 or 2) or Willpower (Imperial City) - Glypth: Truly Superb Glyph of Increase Magical Harm

Staff:
Restoration Staff: Sanctuary (Banished Cells 1 or 2) or Torug's Pact - Glypth: Truly Superb Glyph of Absorb Magicka
Lightning Staff: Sanctuary (Banished Cells 1 or 2) or Torug's Pact (Can Only craft this) - Glypth: Truly Superb Glyph of Shock

Champion Points

For each section (300, 600 &810) try not going passed the assigned value below but distribution to whenever you see fit.

Champion points [810]
The Ritual: 23 Thaumaturge
The Apprentice: 100 Blessed, 72 Elfborn, 26 Spell Erosion, 49 Elemental Expert

The Lover: 85 Arcanist, 85 Tenacity
The Tower: 100 Siphoner

The Lady: 49 Hardy, 49 Elemental Defender, 48 Thick Skinned
The Steed: 81 Ironclad, 43 Spell Shield

Champion points [600]
The Apprentice: 100 Blessed, 72 Elfborn, 27 Elemental Expert, 1 Spell Erosion

The Lover: 70 Arcanist, 70 Tenacity
The Tower: 60 Siphoner

The Lady: 49 Hardy, 49 Elemental Defender, 23 Thick Skinned
The Steed: 61 Ironclad, 18 Spell Shield

Champion points [300]
The Apprentice: 61 Blessed, 40 Elfborn, 1 Spell Erosion

The Lover: 48 Arcanist, 48 Tenacity
The Tower: 5 Siphoner

The Lady: 23 Hardy, 23 Elemental Defender, 23 Thick Skinned
The Steed: 31 Ironclad