Skill-specific critical strike chance in helmet enchantments: how does it work?

So, say we have a helment with an enchantment that says "90% increased Tornado Shot Critical Strike Chance". How does it figure into the total critical strike chance calculation? Is it applied to your base critical chance, same as the regular "increased global critical strike chance" modifiers? Or is it applied to you cumulative critical strike chance shown on the character sheet?

Works the exact same as any other source of increased crit chance - applied to base crit, additive with other crit chance increases.

Thanks, that means helmets with that enchantment are definitely not worth the insane asking price :) Will be looking for an "increased tornado shot damage" mod instead...

If you have a good base crit chance and high multiplier, the 90% crit chance should be better than the 40% increased damage.

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raggapaul wrote:

If you have a good base crit chance and high multiplier, the 90% crit chance should be better than the 40% increased damage.

Hm... My character sheet crit chance is 64.43%, and my crit multiplier is 441%. I'm not sure how to check the base crit chance, though. Is it the crit on my weapon? Then it's 8.85%. So what should I go for - 90% crit chance or 40% increased damage? Both are kind of expensive, so I can't afford to experiment...

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DGTLDaemon wrote:

I'm not sure how to check the base crit chance, though. Is it the crit on my weapon? Then it's 8.85%.

Kinda, basically, yes. At one point in the game, the crit on your weapon was your base crit chance for Attack skills, period (barring secondary-effect skills like Explosive and Caustic Arrow). Since then, there have been ways to add to base crit chance. In order of decreasing likeliness:

1. Increased Critical Strikes Support
2. Assassin's Deadly Infusion
3. Essence craft

I may have missed one.

Thus, assuming your 64.43% is reached without ICSS, then the DPS differential would be:

((1-0.6443-0.9*0.0885)+((0.6443+0.9*0.0885)*4.41)) / ((1-0.6443)+(0.6443*4.41)) = 1.08496, or about 8.5% more DPS

Looks to be about the same DPS differential as you would likely get from 40% increased damage. To figure that out you'd need to know your existing increased x% damage applied to Tornado Shot before adding the 40%, and then do a process that is similar to but simpler than the crit mess up above. For example if you had 400% increased damage applied to TS, and the helm would take you to 440%:

(1 + 4.00 + 0.4) / (1 + 4.00) = 1.08, or about 8% more damage.

For mental calculus'ing the increased damage, you can think "diminishing (proportional) returns." So the more increased damage you already have, the better other options become (i.e. with higher existing increased damage, the more damage from 40% will be lower than 8%; with lower existing increased damage, the more damage from 40% will be higher than 8%).

Let's try, assuming you have level 20 ICSS on top of your weapon:

((1-0.6443-0.9*(0.0885+0.019))+((0.6443+0.9*(0.0885+0.019))*4.41)) / ((1-0.6443)+(0.6443*4.41)) = 1.10319, or about 10.3% more DPS.

EDIT: You can also use algebra to figure out what the "equivalent increased damage breakpoint" would be.

Plug into WolframAlpha:
(1+x+0.4)/(1+x) = 1.10319

gives us

x = 2.876

So at 287% increased damage and below, 40% damage is more preferable than 90% increased crit chance at your crit level plus an assumed 8.85% base crit plus a 1.9% increased crit gem. At 288% increased damage and above, you would prefer the crit chance assuming it's 8.85% plus a 1.9% increased crit gem.

@adghar wow, thanks for the detailed explanation :) Now I can at least make an informed choice. Which probably will be in favor of 90% increased crit, because for some reason helms with 40% increased tornado shot damage are much, much more expensive.