How thorns (dual blader) works

So I asked Spadow over at his blog about this, particularly the Aran, Evan, and Viper/Buccaneer part. Here's a more accurate translation:

Thorns Effect

Dual Blade
-35% chance of performing a critical attack, Skill damage 250%
ex) Upper Stab’s damage without crit is 245%, but with crit it is 495%

Magician
-35% chance of performing a critical attack, damage multiplied by 2.24
ex) Genesis’s damage without crit is 99999, but with crit you can make it to 199999

Thorns Effect will not work on classes who have a critical skill (Night Lord and Archer)

Thorns Effect will work on classes who don’t have a critical skill (Captain, Shadower, Hero, Paladin and Dark Knight)
-35% chance of performing a critical attack, Skill damage 125%

Viper
- Thorns Effect will only work when you attack stunned enemies

Aran
- Thorns Effect will only work when you’re gaining combos

Evan
- Can be affected by Thorns Effect

I'm going to assume that what they mean by "Aran's Thorns Effect will only work when you're gaining combos" is that Thorns will only be in effect if Combo Critical's effect is lower than Thorns' effect.