[Snake]

You're just unlucky. That's the only reason why I'd vouch against making wounds more rare than they are. At most we're working with the same chances of dropping a 10* item. (generally 0.5%~1.5% per damage proc, but mostly based on how big it is vs enemy DEF/RES)

Anyway:

Cut: Lingering Slash damage equal to WL*10 (meaning 50 damage at crippling)
-- This is alright.
Stab: Lingering Pierce damage equal to WL*10
-- This is alright.

Concussion: Reduce Hit and Evade by WL*5+confused at WL 3 and higher(?)
-- This is not alright. I'd say this should grant both Worn Out LV15 and Clumsy with permanent duration on battle start. The mentioned debuffs are more fitting for ruptured ear.

Burn/frostbite: reduce elemental resistance 5+WL*5
-- This is alright, but it should be 'all' elemental resistances, and they stack together.

Acid Burn: reduce Armor/Magic armor by WL*2 (or Def/Res, whatever)
-- DEF/RES, yes.

Ruptured Ear: Reduce evade versus attacks behind you WL*5 (cause can't rely on hearing? clearly you also gain sound resistance cause you can't hear stuff)
-- Reduce Hit and Evade by WL*5 and inflict Confusion permanently on battle start. Then, certain hearing-based effects are prevented from targeting you such as Blind Fighting, Charisma (Motivate), Convert, etc.

Ill Will: Whenever you use a rage-based effect, you are inflicted with Confusion for 2 rounds.

Fever: Reduces all your status by 50%. Makes you sneeze every round end, inflicting Hesitation/Fear on all enemies around you.