Hello guys,
can anyone help me with calculation of dmg for my fire dru - i need to compare Ravenlore -20% fire base with facet 5/5 and flickering flame -14% with +2 armageddon/fissure/volcano.

So roughly is +2 skill inferior to -11% res and 5% dmg (i assume it is)?

Assume that the average fire Res on a non immune monster is 50%. If you go with -20% res, you'd be doing about 40% more damage than you would if you did the same damage dealt without the res reduction.

-14% would be about 28% more damage, but you get the scaling from the +2 skills. I would still guess that -40 does more even without the scaling, making Ravenlore more ideal.

I would say it depends on cost, where you farm, how much negative res you actually have without either FF or RL on hand. If you have no -Res, go with Ravenlore. If a -20 res Ravenlore + Facet is substantially more expensive than a Vex, then go with FF.