Heal Catalyst
The Giver's and Minstrel's Catalyst: 
Spectacular Sphere gives everyone near the jade sphere quickness and a boon, and 
Sphere Specialist makes it last.
This is a boon build. It heals, but what you are paid for is uptime — the sphere, the auras, and everything 
Concentration stretches.
Why these traits
Spectacular Sphere is why you take the spec: a larger jade sphere that hands nearby allies quickness and a boon matching your attunement each time you activate it. Sphere Specialist lengthens those boons and lets you keep building energy while a sphere is already out. 
Energized Elements pays energy and boons for swapping attunement, and swapping is also what triggers 
Rock Solid (
Stability on the earth swap) and 
Cleansing Wave (a cleanse for nearby allies on the water swap). 
Powerful Aura sends every aura you give yourself to the squad and 
Elemental Shielding adds protection to each one — 
Soothing Ice and 
Elemental Epitome are where those auras come from.
Gear reasoning
Giver's and Minstrel's with 
Water and two Concentration: boon duration is the output, so it is what the gear buys. 
Benevolence stacks a healing-to-allies bonus off kills and 
Frenzy refunds two seconds of recharge on every equipped skill when something dies. 
Karakosa heals nearby allies whenever you blast a field — and your own sphere is a field.
When not to run it
It is not a healer. If the squad is taking more damage than it can outlast, Heal Tempest and Heal Evoker are built for that and this is not.
Your energy also only comes from striking foes (
Depth of Elements), so a Catalyst that spends the fight running has nothing to drop. Bring this when boons — quickness in particular — are the thing the squad is missing.