I know it's been confirmed that healing is multiplicative, but are all stats like this? Or just healing for balance purposes?

The reason I ask is my critical heavy Kael.

It shows my Kael has a base critical strike chance of 15%, with a gear based +59% shown. And one of his skills (Acid rain) says it has a 15% increased chance of critical strike.

So is this a 15% + 59% + 15%? (Straight Additive) (~27.4% crit rate)

Or a 15% x 1.59% x 1.15%? (Straight Multiplicative) (~89% crit rate)

Or maybe a (15% + 59%) x 1.15? (Gear and base stats additive, ability effect multiplicative) (~85% Crit)