Heal Specter
A Minstrel's Specter healing the squad through Wells — every Well is a shadowstep, so the heal lands where you aim it, not where you stand.
Double Scepter/Pistol means a weapon swap never costs you the kit. 
Shadowfall is the pull you save for the push; the rest of the bar is healing, boons and cleanse, all of it delivered as a Well.
Why these traits
Steal becomes Siphon on Specter, and it is the engine. 
Thrill of the Crime puts 
Fury, 
Might and 
Swiftness on nearby allies every time you land it, 
Bountiful Theft adds 
Vigor and rips the target's boons across to your side, and 
Shallow Grave transfers your conditions onto them while cleansing the allies around you — a cleanse, not a downed-state save. 
Sleight of Hand shortens the recharge so all of that comes round again sooner.
Traversing Dusk is what makes the Wells work: each one shadowsteps you, and every shadowstep heals the allies you land next to, while the Wells themselves grant 
Resistance on impact. It is not a mobility trait — the movement is in the Wells already.
Dark aura is the other loop. 
Shadow Savior gives you one on Siphon and heals nearby allies for it, 
Shielding Restoration hands allies barrier and dark aura when you use a heal skill, and 
Cover of Shadow strips a condition off nearby allies each time you take dark aura yourself. All three are ally-facing; none of them is self-sustain. 
Shadestep then layers extra ally effects onto the Shadow Shroud skills.
Gear reasoning
Full Minstrel's — toughness, vitality, healing power, boon duration, and nothing that makes you hit harder. Your contribution is uptime.
Monk is a flat healing-power and boon-duration rune, nothing conditional. The actual outgoing healing multiplier is 
Transference, which is why it is on both sets, with 
Dark Sentry adding more of the same for free.
Karakosa heals nearby allies when a blast finisher combos a field — and this build supplies both halves itself. Every Well is a dark field, and 
Shadow Sap on Scepter is a blast finisher. Blast your own Well; standing in it does nothing for the relic. 
Frenzy and 
Life are the kill-reward fillers.
When not to run it
This is a zerg build and the gear says so: Minstrel's is toughness, vitality, healing power and boon duration, with no offensive stat on it at all. In a small havoc group you will out-sustain the enemy and still lose the fight, because nobody is killing anything.
It also gives the squad exactly one 
Stability skill — 
Mind Shock, on the Shadow Shroud bar, so it costs shadow force to reach. If holding Stability up is the job, take Chronomancer instead.