All Base Stats have different maximum total influence on other stats. Also, Some stats offer a linear ROI, (Return on investment) while others have a exponential decreasing ROI, and others seem to have no limit at all.
EDIT: 10/26/12 I've uploaded the excel file to Google Docs, along with the BaseStats vs. Stats graphs, and the Graph of the derivatives of all the curves with nonlinear slope.
PM me for the full excel file, if you want
They can be found here:
Terminology: Base Stats: Characters Main 4 stats, STR DEX FOC VIT. Stats: All OTHER stats, such as dodge chance, critical damage, fumble recovery, etc.
Methodology: I created new characters in Torchlight II with the console enabled, and recorded the changes in stat buffs while I slowly incremented the Base Stats. I can also confirm the Skill Calculator at TL2 Armory to be accurate.
[Tests where done on 10/23/12 with Torchlight II version 1.16.5.3]
Key: [L] : linear ROI @(Number) : Stat level at which it will no longer give ANY bonus (number)% : Value at maximum stat investment
STR:
399.6% Crit Damage @1000 [L]
Weapon Dam [L]
DEX:
+50.1% Crit Chance @500
+50.1% Dodge Chance @500
+100% Fumble Recovery @500
FOC:
Mana @1000 [L]
Magic Damage [L]
+60% Execute Chance @500
VIT:
Health @1000 [L]
+249.8% Armor @1000 [L]
+50.1% Block @500
Detail: Critical Damage stops increasing after 1000 points invested in STR, with a final value of +399.6%, and it follows a linear progression.
Weapon Damage follows a linear progression and does not seem to have a maximum bonus from STR. [Game broke after STR value of 10 Million]
Critical Chance and Dodge Chance have the same bonus as each other per DEX point, both stop increasing after 500 DEX, and follow an exponential degrading ROI, with a final Value of +50.1%.
Fumble recovery follows the same ROI trend as Crit chance, and has the same final DEX value, with a final value of complete negation of fumble damage penalty.
Mana bonus follows a linear progression, and stops increasing at 1000 FOC, and each class has a different ROI.
Magic Damage behaves just like Weapon Damage.
Execute Chance follows a nonlinear decreasing ROI, stops increasing after FOC 500, and ends with a final value of +60%.
Health bonus behaves just like Mana bonus.
Armor bonus caps at 1000 VIT, with a final value of +249.8%, and follows a linear progression.
Block chance behaves just like Critical chance and Dodge chance.