Power Tempest (Hammer)
The Hammer Power Tempest: Air and Water rather than Fire, so your auras go to the squad and the people next to you get healed.
It is the only one of the four power variants on a different specialization line, and the only one carrying 
Lightning Flash. Different multipliers, not fewer.
Why these traits
The Water line is why this variant exists. 
Powerful Aura gives every aura you grant yourself to nearby allies — and 
Unstable Conduit produces one on every overload — which is also the only thing that makes 
Tempestuous Aria's damage bonus fire, since it pays out on granting an aura to an ally. 
Piercing Shards and 
Flow like Water are the damage: more strike damage against vulnerable foes, doubled while you are attuned to water, and more strike damage while your own health is up, plus a heal every time you block or evade. Air still supplies 
Fresh Air and the crit package. There is no Fire line here, so no 
Power Overwhelming and no 
Persisting Flames.
Gear reasoning
Dragon's and Marauder under 
Scholar — power and ferocity from the rune, vitality from the prefixes. The sigils are the same damage package as the rest of the family: 
Force on both sets, 
Impact against stunned and knocked-down targets, 
Bloodlust for power off kills, 
Fireworks on your long-recharge weapon skills. Nothing here is healing power, so the group healing you do bring — 
Soothing Mist and 
Healing Ripple from the Water minors — is a bonus, not a job.
When not to run it
The Water line's damage is conditional: Piercing Shards wants the target vulnerable and you in water, Flow like Water wants your own health high. If the fight lets you stand at the back untouched, you are paying for sustain you never use.
In that fight, Power Tempest (Staff) has the reach and Power Tempest (Spear) has the Fire multipliers.