Righteous Fire

Now that's neat.
However, I believe the actual RF effect is a "turn on" effect, instead of sustained, so it won't shut off if you switch out the gem.

So, given that you can't deal damage with RF...
How about damage to yourself?
Edit: Nvm, it's a multiplier, not an increase. Pointless.

Does having more ES make you take more burn damage? or does the ES burn only apply to your own ES?

I had a lot of thoughts about rightous fire and must honestly say i don´t like the skill very much. Main reason for this is that you need a highly perfected and expensive build for it. But as far as i know there is no use for this skill below level 65.

So why not make the gem simillar to arctic armour for example. If you want the high damage aoe it has now you still need to level it to lvl 20 but then also have the same drawback it has now. For a level 1 gem i would propose "enemies burn for 2 % of your life and your es", "you burn for 6 % of your life and 4 % of your es" and "spell damage increased by 5 %"

This would mean a high level char with around 5000 HP would burn enemies with around 100 fire damage per sec and need to deal with 300 dps fire himself (with 75 % res 75 dps, thats tankable). For a char that has 5000 HP i would say that 100 dps isn´t that much and also the spell damage isn´t a so high buff. But at least it would give the possibility to some nice but not op flame surge builds.

does AA mitigate the damage from RF?

I have a lvl 17 PoF, for a max amount of 87 fire res.
I have 4.6K life.
12.7% life regen.

I still can't sustain RF... What am I doing wrong?

post passive tree? you didn't take increased buff effect nodes did you?