DPS Healer Build

• Cephaliarch's Flail - an AoE spammable that generates Crux, heals you if you hit any enemy and increases the damage enemies take from you by 5%
• Pragmatic Fatecarver - extremely powerful Crux spender that deals full damage in AoE, has massive range of 22 meters and grants you a big damage shield while you channel it.
• Recuperative Treatise - an ability that deals decent damage, ensures you'll have at least 1 Crux when your beam ends and improves your sustain.
• Budding Seeds - extremely strong and cheap AoE HoT, which can also be recast to be used as a direct heal when needed. It will improve your sustain by proccing the Nature's Gift passive.
• Camouflaged Hunter - this ability will grant you the Minor Berserk buff which increases your damage done by 5% for 5 seconds after you deal Critical Damage from enemy's flank, which has a very wide radius. It will also trigger the Slayer passive, increasing your Weapon and Spell Damage by 3%.
• Crescent Sweep - an ultimate which is slotted only to proc the Piercing Spear passive which increases Critical Damage by 12%. You should only cast it when the battle is about to end, otherwise The Languid Eye is far superior.
• Energy Orb - strong AoE HoT which provides crucial Combustion synergy to your teammates, which restores 3960 of dominant resource up to once every 20 seconds
• Overflowing Altar - this ability applies Minor Lifesteal to all nearby enemies, causing you and your allies to restore 660 Health per second when damaging them. It also provides the Blood Feast synergy which restores 65% Maximum Health to the user
• Soul Burst (Healing, Sage's Remedy, Courage) - an AoE burst heal which applies a 10 second HoT and grants everyone Minor Courage for 20 seconds, increasing Weapon and Spell Damage by 215
• Elemental Blockade - this ability will constantly proc our Weapon Damage enchant. It will also apply Off Balance to enemies who have the Concussed status effect already applied to them
• Echoing Vigor - extremely strong AoE HoT which is going to proc the Powerful Assault set
• The Languid Eye - an Ultimate which deals damage in a small AoE over 6 seconds which can be moved by pressing the ability again (it's off Global Cooldown).

Whenever you need to slot situational skills, replace Soul Burst. For situational Ultimates, replace The Languid Eye

• Soul Harvest - replacement for Crescent Sweep for when you're using Assassination instead of Aedric Spear
• Crushing Shock - a ranged interrupt which you'll need for some fights
• Aggressive Horn - an offensive support Ultimate which grants everyone a 10% Max Resource buff for 30 seconds and Major Force for 10 seconds. The Max Resource buff translates into roughly a 2% damage increase while the Major Force is roughly an 8% damage increase. Use it if your random teammates turn out to be good, because then this Ultimate will be more effective than dealing damage yourself with The Languid Eye
• Reviving Barrier - a defensive support Ultimate which can help your team survive

I don't use a static rotation so this is just a list of priorities. Simply recast abilities when they run out and follow this list of priorities when there are multiple things to refresh

It's impossible to give a definite ruleset of when to keep up your heals. Echoing Vigor is something you should keep up at all times, because it procs Powerful Assault. Soul Burst should be cast at least every 20 seconds for the Minor Courage, but you don't need to keep up the 10 second HoT if there's no damage pressure. Energy Orb has to be cast at least once every 20 seconds for the Combustion synergy.

Priority List

• 1. Recuperative Treatise
• 2. Crescent Sweep/Soul Harvest if the fight is about to end and you won't get enough Ultimate for another The Languid Eye
• 3. Elemental Blockade
• 4. If you have enough Ultimate use The Languid Eye
• 5. If you're not at 3 Crux yet use Cephaliarch's Flail
• 6. Pragmatic Fatecarver

Pre-buff

These abilities can be pre-cast before entering combat

• Recuperative Treatise

Other Monster Sets you could use instead of Nerien'eth if you want to lean even more into Support rather than Damage

• Ozezan the Inferno - grants your teammates 4272 Armor and Minor Vitality, increasing their Healing Received and strength of Damage Shields by 6%. The armor should provide roughly 9% damage mitigation
• The Blind - provides lots of Damage Shields and the 1-piece bonus of it is Critical Chance which will boost both our DPS and Heals
• Symphony of Blades - grants your teammates sustain. However, due to the nature of random queue, most people will balance the sustain of their builds without Symphony in mind, because they can't know for certain that their Healer will run it. Because of that, using Symphony in random queue is usually pointless

Additional tips

• You can use Shock enchant instead of Poison or Flame if you want to provide the Concussed status effect yourself. Concussed is needed to proc Off Balance with Lightning Elemental Blockade, but it should usually be provided by the tank, or by the DDs if they're doing Shock damage