Projectile weakness vs Elemental weakness

Lets say I'm doing only ranged elemental damage and approximately 100 dps without using any curses.

What will be my dps if I use a curse that reduce monsters'e elemental resistance by 45% (elemental weakness)?

Now, what will be my dps if I use a curse that increase projectile damage by 30% (projectile weakness).

To stay focused on my question, let's ignore the other effects of the actual curses.

I started doing some maths, but then I realised that in the case of negative elemental resists (-x% resist), this is equivalent to saying that damage is increased by +x% (it's not the case when the value is negative, then final damage is multiplied by (1-x/100).

So if the damage is pure elemental, and the monster had 0 resist to start with, then elemental weakness increases damage by 45% (for a total of 145 DPS), and projectile weakness by 30% (for 130 DPS). So elemental weakness wins in that case, but only if the damage was of an elemental type to start with.

If the monster had element resistance though (like a yellow monster with "resist cold"), then it's different. I don't know what the %resist of the monster is in that case, but I believe it's around 50% (from experience as an Ice Witch). Then a spell projectile of 100 DPS would be reduced to 50 DPS, but with elemental curse the monster's resist would be 50% - 45% = 5%. So final DPS would be 100*(1-5/100) = 95 DPS.

If you had used projectile weakness instead on this 50% resist monster while firing a 100 DPS spell, damage would have been 100*1.3*(1-50/100) = 65 DPS.

So in the case of elemental resistant monsters, elemental curse wins when the projectile is a spell.

Edit: Also I think your number of 45% elemental weakness a bit over the top since my level 15 gem after beating merciless is only 44%.

Ok, interesting. Now lets add another possibility : Critical weakness.

In the same scenario of ranged elemental damage of 100 dps, including 50% chance to crit and 300% damage on crit.

Vs 0 resistance monsters

Elemental weakness (-45% resist) : 145 dps

Critical weakness (+9% crit chance, +65% crit damage) :

50% of the dps is increased by 65%, so (100 * 0.5 * 0.65) = 32.5 dps.

9% of the dps is now multiplied by 365% instead of 100%, so 100 dps * 0.09 * 3.65 = 32.85 dps

The final dps to a 0% resistance monster cursed by critical weakness would then be : 100+32.5+35.85 = 165.7 dps

Vs 50 resistance monsters

Elemental weakness (-45% resist) : 95 dps

Critical weakness (+9% crit chance, +65% crit damage) :

50% of the dps is increased by 65%, so (50 * 0.5 * 0.65) = 16.25 dps.

9% of the dps is now multiplied by 365% instead of 100%, so 50 dps * 0.09 * 3.65 = 16.425 dps

The final dps to a 50% resistance monster cursed by critical weakness would then be : 50+16.25+16.425 = 82,675 dps

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In conclusion, avantage to critical weakness against normal monsters and avantage to elemental weakness against resistant monsters.

The deciding factor would then be what % of monsters are resistant to elements.

If it's 50% or less, then critical weakness would generally be superior, if we ignore other attributes of elemental weakness, that is.