Power Evoker
The Spear Evoker: 
Burning Precision keeps foes burning, and almost every damage trait in the build is paid for burning targets.
Fire and Air for the multipliers, the Evoker line for the familiar. It keeps its attunements — this is not the Heal Evoker's locked-in build.
Why these traits
The whole build is paid in burning. Burning Precision makes your critical hits burn; 
Fiery Might, 
Pyromancer's Training and 
Persisting Flames then all hand you extra strike damage for it. 
Galvanic Enchantment feeds the same loop from the Evoker side: after a familiar skill your next strikes arc chain lightning, and evoker chain lightning inflicts burning. 
Power Overwhelming and 
Bolt to the Heart are the flat multipliers underneath, and 
Raging Storm keeps fury — and so the ferocity — up.
Gear reasoning
Marauder and Dragon's under 
Scholar. The rune is flat power and ferocity, so every point of vitality this build has comes from the prefixes. 
Force on both sets is 5% damage; 
Impact adds 3% and another 7% against stunned or knocked-down foes, which is what your squad's crowd control is for. 
Bloodlust stacks power off kills, and 
Fireworks pays out on weapon skills with a recharge of 20 seconds or more — the Spear etchings are 25.
When not to run it
Light armour, no 
Stability, no blink: this bar is 
Arcane Echo, 
Glyph of Storms and 
Signet of Fire, and it leaves both 
Armor of Earth and 
Lightning Flash behind.
Your damage also depends on the target burning. Against a squad with heavy cleanse, or one that reaches you at all, Power Tempest (Hammer) keeps a blink and does not care whether anything is on fire.