Originally Posted by Funinyourgame
Sorry for the misunderstanding, for me SAG (sagesse) wich is in french is WIS (Wisdom) in English.
Ah, French. Sagacity wasn't far off at all, then. Should have gone with my instinct.
The introductory paragraph says the class combines the styles of the fighter, rogue, barbarian, and scout. However, the class itself feels more like a fighter with a rogue twist.
To fix that, you could make a feature sort of like sneak attack fit into internal damage. For example:
Underhanded Blow (Ex):
At 2nd level, the breaker is able to catch an opponent off guard and force them to pay. If the breaker attacks an enemy who has been denied their Dexterity modifier to AC, the penalty and DC for internal damage increase by 1.
This adds tactics to the breaker while enforcing the main feature, internal damage.
Here's another, along the lines of the scout:
At 4th level, the breaker can move and attack in one fluid motion, leaving destruction in his wake. If the breaker moves 10 feet or more in one round and then attacks, he deals an additional 1d6 damage.
At 8th level, and at every fourth level after (12th, 16th, 20th), the damage increases by 1d6.
You could then expand on that, adding an ability along the same lines at a higher level that adds even more depth.
Powerful Momentum (Ex):
At 9th level, the breaker's ability to attack while on the move improves. If the breaker moves 20 feet or more in one round and then attacks, he not only deals bonus damage, but also may attempt to bull rush or trip the enemy at a +4 bonus. If the breaker fails to trip, the target does not get a trip attempt in return.
This leaves 3rd level as a purely dead level, so let's try to fill that in with an aspect of the barbarian.
At 3rd level, a breaker is capable of entering a state of peace as a free action. During this time, the breaker gains a +4 bonus to Wisdom and Will saving throws. In addition, internal damage's save DC is increased by 2 for the duration. This state lasts for a number of rounds equal to 3 + the breaker's (newly improved) Wis modifier. Upon leaving this state, the breaker's introduction to the harsh world leaves him sickened for 3 rounds or until the end of the encounter, whichever ends first.
A breaker can enter this state of peace only once per encounter. At 3rd level, he can use his serenity ability once per day. At 7th level, and at every fourth level after (11th, 15th, 19th), he can use it one additional time per day.
This gives some more flavor to the class and fits in the final class of the four you listed. That leaves only a couple of dead levels in the class. I'm kind of out of ideas, though. Maybe you'll think of something. Otherwise, just leave them dead.
I strongly urge you to create a capstone, however. Again, there should be incentive to take this class to level 20.