Deathfire Touch is REALLY underwhelming.
In what case would you pick this over Thunderlords? Thunderlords is basically another ability in itself, whereas Deathfire is just a really shitty version of Ignite. Every other keystone has their benefits; Warlords for Lifesteal and re positioning, Fervor for constant damage, Stormraiders for re positioning and slow resistance, Thunderlords for burst, windspeakers for OP heals, Grasp for lane sustain and favorable trades, Courage for OP shields and benefits tanks for initiating, and Bond of stone for constant healing. Then we got Deathfire which burns for 8 damage per second, if you're lucky. Rework this shit man.
is pretty much my premier example. He scales out of control and drops like 200 damage DFT late on his W, which is just swell.