(Haven't tried this build yet, so take everything I say with a grain of salt.)
For class, go White Mage and choose Overflowing Health and Holy Champion at the perk branches.
For stats, go with Toughness, Willpower, and Cunning. Use the Presence boon when you can.
For equipment,
| Primary | Free Slot, Flametongue Blade | Catalyst, +10 Crit and +5 Spellpower
We want those two stats, so feel free to switch to any weapon that has those |
| Offhand | Thornshield | Gain Defending and Thorny (scales with Spellpower) when you are crit'd |
| Head | Helm Of Heroes | +10 Leadership |
| Neck | Heart Of Oak | +5 Crit and +30 Armor |
| Shoulders | Seaweave Shaman's Cape | Immunity to Sunder |
| Armor | Conqueror's Breastplate | +20 Leadership, generate 10% more Threat |
| Waist | Evergreen's Bountiful Bag | 20% increase on self heals |
| Hands | Golden Carrot Bracelet | +3 Crit and +25 Crit Effectiveness when HP>75% |
| Feet | Free Slot, Weed-walkers | +5 Spellpower, feel free to switch this |
| Ring | White Blossom Ring | +5 Crit
When you crit or crit heal, give enemies Willpower/3 stacks of Resonance and Staggered |
| Ring | Free Slot, Hornet Ring | Hornet Ring would be BiS, but if the curse is too much then check out other crit rings |
For powers,
| At-Will | Recharge | Recharge | Encounter | Ultimate |
| Lay on Hands | Blessing | Primal Scar? | Summon??? | Inspiration |
| Heal that can transfer Threat from you companions to you or give Threat when use on self | Attack buff for party | AoE Debuff for Fire, Storm, and Frost damage
Feel free to switch around spells | Anything really? Haven't thought about powers too much
Summon can bring in the extra damage you lack | Full party heal and increases max HP |
You Crit Heal to give enemies Resonance and Staggered, which in turns gives a small party heal, which will happen ~50% of the time.
You take DPS companions who no longer have to worry about threat since you'll just heal them and transfer it over to yourself.
With your Leadership through equipment, you give +30 to all attack stats to your companions and more while you have the Presence boon.
As a slight bonus you do passive thorn damage whenever you are hit by a crit.
You won't do too much damage, but you have your Recharge and Encounter slot to put some damage spells in.
Might be fun since you're a tank and healer support wrapped in one, might make fights a slog since you'll lack damage.