What is the Radius of Righteous Fire

1 micron?
1 meter?
1 foot?
1 furlong?
1 yard?
1 cubit?
1 pixel?


Is it a multiple of the above?

Just trying to get an idea of whether or not to invest heavily in AOE radius increase nodes or if its a waste.

It's a waste. Most RF builds want to minimize the burning damage to take advantage of the spell damage bonus with less drawbacks.

%reduced life to reduce the burning damage you take
Zealot's Oath will apply your life regen to ES
You can reserve health for auras using blood magic to put yourself into "low life"
You can get items like Spring Leaf to increase life regen ( which will be applied to ES ) on low life
Shavronne's will prevent chaos damage from bypassing your ES to prevent insta-deaths from having low life with chaos damage
Pain Attunement will add another more spell damage modifier because you're on low life

That's pretty much how it's used now, as an insanely good damage boost, but it's very gear-dependent.

EDIT: Oh, and increased maximum fire resist will help a lot. You can get it from the purity aura and the Elemental Adaptation passive as well as Ruby Flasks ( which is good with a Surgeon's affix ).