Power Tempest (Spear)
The Spear Power Tempest: 
Fresh Air recharges air on a critical hit, and 
Transcendent Tempest pays a damage bonus for every overload you finish.
Fire, Air and Tempest on Berserker's, Dragon's and Marauder. It shares that trait core with the Staff and Wildfire variants; the Hammer one runs a different one.
Why these traits
Fresh Air recharges your air attunement on a critical hit and gives you ferocity each time you re-attune, which is what makes the air burst repeatable rather than a one-off. Transcendent Tempest shortens the wait for 
Singularity and hands you a damage bonus for completing an overload; the 
Hardy Conduit minor means those overloads also drop protection on nearby allies. 
Power Overwhelming and 
Persisting Flames are the Fire multipliers, and both want you in fire and keeping things burning. Two of the majors do very little here: 
Conjurer only gives you a fire aura when an ally picks up a conjured weapon, and the only conjure you carry is 
Conjure Fiery Greatsword; 
Tempestuous Aria pays out on shouts and on granting auras to allies, and this build has neither.
Gear reasoning
Berserker's, Dragon's and Marauder with 
Deadeye — power, ferocity, precision, no boon duration and no healing. 
Force on both sets, 
Impact for the extra 7% against stunned and knocked-down targets, 
Bloodlust to stack power off kills. 
Fireworks pays out on weapon skills with a recharge of 20 seconds or more, so it rewards the Spear etchings — 25 seconds each — and not your autoattack.
When not to run it
No 
Stability and no blink on this bar: 
Arcane Echo, 
Glyph of Storms and 
Signet of Fire, with 
Armor of Earth and 
Lightning Flash both left behind. Overloads are channels, so being pushed onto costs you the payout as well as your health.
If you expect to be reached, Power Tempest (Hammer) keeps Lightning Flash and puts Water underneath instead of Fire.