Fire Trap (and general) Mechanics Questions

I've looked everywhere and can't seem to find answers to any of these questions.. so here goes.

1. I know that increased modifiers are additive, but are all of the damage modifiers separate (e.g., base damage * (inc spell dmg) * (inc elemental damage) * (inc fire damage)...) or are they all lumped together (e.g., base damage * (inc spell dmg + inc elemental damage + inc fire dmg...)). So for example, if I were to want to use fireball and have 100% inc spell damage and 0% increased fire damage, and I had the choice of getting 15% more spell damage or 10% fire damage.. the fire damage would be better if all of the modifiers were separate, while the spell damage would be better if everything was lumped together.

2. Is ignite damage based on the damage that is actually dealt to the opponent, or is it based on the value before resistances? So if I were to support fire trap with fire penetration (no quality), I know that fire penetration will only apply to the initial explosion (not the ignite if that happens).. but will it still indirectly increase the ignite damage because that is based on 20% of the initial hit?

3. Does burn damage "double dip" with fire damage? So for example if I were to deal a fire trap that would do 100 damage before any modifiers, with 10% fire damage it would do 110 damage.. 20% of that (ignite) is 22.. and my question is if that is it, or is that 22 also increased by that 10% fire damage for a total of 24.2 ignite dps?

Or if there is a way to view a damage log, that would make my own testing much much easier. Thanks in advance :)

1) they stack additively
2) It's based on the damage dealt but is also effected by resists. So if the target has 50% fire resist, and you hit it for a 200 damage fire crit, it'll take 100 initial damage, and burn for 40 damage over 4 seconds. Fire Pen will indirectly increase the damage of the burn, and Flammability will both indirectly and directly increases the damage of the burn.
3) Yes

This is how I understand those things to be, please feel free to correct me if I'm wrong (sources would be awesome as well)

Side note, Vulnerability is (effectively) multiplicative with any other source of burn damage increase you may have (passives, searing touch, inc burn damage support), but additive to any other damage increase maladies on the target.

Thanks for your reply. Just to clarify, for my first question, you mean that everything is lumped together, correct? So if you had 100% inc spell damage and 0% increased fire damage, I would still benefit more from 15% increased spell damage instead of 10% increased fire damage? I was just looking at vulnerability on the wiki, and it states that, "Cursed enemies take increased damage: Because these modifiers are an increase to the target's damage taken, they are multiplicative with your damage dealt and additive with any other increased damage taken effects on the target". This is really what my first question was about, obviously there are some things that are separate (damage taken is not simply added to spell damage), I'm just wondering which modifiers are separate. Another example could be if I had 100% increased burning damage, and I had the choice of going for holy fire (total of 60% increased burning damage) or entropy nodes (total of 45% increased damage over time), if burning damage was multiplied by damage over time entropy would be better.. if it were simply added then holy fire would be better. Perhaps vulnerability is the only "separate" thing?

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Aderp wrote:

Thanks for your reply. Just to clarify, for my first question, you mean that everything is lumped together, correct? So if you had 100% inc spell damage and 0% increased fire damage, I would still benefit more from 15% increased spell damage instead of 10% increased fire damage?

Remember though, Fire Damage double-dips for the Burn, so 10% Fire Damage would actually be better in that case. ~.^

Thanks for the replies, (especially Vipermagi), they were very helpful. So I would assume that if fire damage "double dips" for initial damage as well as burning damage, spell damage would do the same? I've heard several people assert that burning damage "double dips" (without much certainty), but it just doesn't seem to fit the very literal skill descriptions I've been reading. Has anyone tested themselves or have a link to a source?