Shakir (found in the Salazad Palace) can give some amazing information on a character's ability to survive in combat. For every level a skill is trained, it adds an amount to either attack or defend.
Shakir, attack
All Armor = +1 attack/+1 defend
Precision Attacking = +.5 attack
Longsword = +1 atk/+.16 def
Scimitar = +1 atk/+.5 def
Dagger = +1 atk/+.16 def
Shakir, defend
All Armor = +1 attack/+1 defend
Kite Shield = +.75 defend
CI = +.5 defend/+2 Fatigue
Druid Staff = ~.79 def
Druid Dodge = ~.21 def
Wizard Staff = ~.23 def
Wizard Dodge = ~.77 def
Sorcerer Staff = ~.79 def
Sorcerer Dodge = ~.21 def
Witch Staff = ~.89 def
Witch Dodge = ~.11 def
Plate Armor Knight Dodge = ~.01 def
AGL Warrior Dodge = ~.48 def
Assassin Dodge = ~.84 def
Shakir, fatigue
CI = +.5 defend/+2 Fatigue
Fatigue factors are determined by a large number of variables. The most obvious is the gear you are currently wearing: heavier gear means higher fatigue. Combat intensity (CI) is the more common reason, as for every level of CI you have activated you have 2 fatigue factors added. The other information Shakir gives you on fatigue is your Fatigue Recovery Rate (FRR). This is entirely determined by your maximum stamina, found by dividing your stamina by 8 (rounding down) and adding 1. For example, if you start with 16 constitution (CON) you begin with 112 stamina. 112/8 = 14 + 1 = 15. So you would start with 15 as your FRR.