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At Level 30, I can reach a value of 71 in Defense.
Character:
Starting Attributes:
Strength (STR): 10
Leftover points go here
Dexterity (DEX): 16
Then increase every fourth level, yielding 7 increases at Level 30
Constitution (CON): 15
Why put any points into CON if we don't care about Hit Points? Implants in KotOR2 now depend on Constitution.
Why 15? Over the course of the game, conversations with your companions can yield three3 +1 bonuses to Constitution.
Intelligence (INT): 8
Wisdom (WIS): 16
Stat increases from companion conversation can provide +6 to Wisdom
Charisma (CHA): 8
Light-Sided: Better Name Crystal
To gain all bonuses from companion conversations, you will have to make some Dark Side choices.
Classes
Jedi Sentinel: 15 Levels
Jedi Guardian has the same Defense bonus, but Sentinel also give the immunities to Fear, Stun, and Paralysis, which fit better with a defensive character
Jedi Weapon Master: 15 Levels
All of the Prestige Classes have the same Defense bonuses
Male: To gain the Battle Precognition Power from the Handmaiden, which adds your Wisdom Modifier to Defense.
Feats
Dueling1
Power Attack: No Defense penalties (and decent Damage output, too)
Finesse: Melee Weapons
Does not affect Defense, but an obvious choice for a character like this. Note that Finesse for Melee Weapons implies Finesse for Lightsabers as well, though you can gain Finesse: Lightsabers from an in-game conversation midway through the game.
Equipment
Implant: Quickness D-Package (+4 DEX, +1 Defense2)
Head: Circlet of Saresh (+5 WIS)
The Target Assessor is a nice alternative for characters without Battle Precognition or for those who want to sacrifice a bit of Defense for a bit of Attack (+2 DEX, +2 Attack)
Hands: Improved Automation Gloves (+5 DEX)
Armband: Vao Armband (+1 DEX)
Belt: Aratech Echo Belt (+4 DEX)
Robes: Ossus Keeper Robe (+4 WIS, +1 Defense2)
For Robes, any Defense bonus counts toward the cap of 102. For Armor, the Defense bonus includes an Armor bonus, which does not count toward the cap.
The Matukai Adept Robe (+2 DEX, +1 Defense) works well for characters without Battle Precognition.
Lightsaber: Only a single Saber1, and only the Name Crystal matters, because the game only takes the highest of multiple modifiers for the same Attribute. (+5 DEX, +6 WIS)
Assume the Name Crystal at Level 30
Even though for playing purposes, this is probably not a realistic scenario because you can't upgrade the Crystal once you have found all of the Jedi.
Why not throw a Fencing Emitter (+2 Defense) in there anyway, to offset any Defense penalties2? In any case, I think it's the best emitter for offensive characters as well.
Active Force Powers
Master Valor (+5 DEX, +5 WIS)
Master Speed (+4 Defense)
Force Armor (+6 Defense)
Calculation:
Base: 10
Class: 14
Jedi Sentinel: 6
Jedi Weapon Master: 8
Dexterity: 18 (from the modifier for 47 DEX)
Base: 23 DEX
Start: 16
Level Stat increases: 7
Quickness D-Package: +4 DEX
Improved Automation Gloves: +5 DEX
Vao Armband: +1 DEX
Aratech Echo Belt: +4 DEX
Name Crystal: +5 DEX
Master Valor: +5 DEX
Wisdom: 16 (from the modifier for 42 WIS)
Base: 22 WIS
Start: 16
Companion conversation increases: 6
Circlet of Saresh: +5 WIS
Ossus Keeper Robe: +4 WIS
Name Crystal: +6 WIS
Master Valor: +5 WIS
Dueling: 3
Powers and Effects: 102
Quickness D-Package: +1 Defense
Ossus Keeper Robe: +1 Defense
Lightsaber (Fencing Emitter +2 Defense
Master Speed: +4 Defense
Force Armor: +6 Defense
Because this list totals 14, the character can absorb -4 in Defense penalties before lowering his total Defense.
Notes:
1: Initially, you would assume Dueling would provide the highest bonus, since it grants +3 to Defense with Master Dueling. But then, you realize that Lightsaber upgrades can provide Defense bonuses, and that a Fencing Emitter and a Lorridan Gemstone together will result in a Defense bonus of +4. But, then you realize the game caps Defense bonuses from Items and Effects at 102, and you can reach that with Force Powers alone. And Lightsaber Crystals do not provide sufficient bonuses to Wisdom or Dexterity to overcome the +3 from Dueling. So, Dueling does indeed provide the highest ceiling for Defense.
2: I could only see the cap of 10 Defense from Items and Effects in-game, but it seemed to accord with the rules from KotOR. However, any bonuses in excess of 10 can offset any penalties from Attack types like Critical Strike (-5 to Defense) or detriments from Effects like Slow.
3: You can actually achieve four +1 CON bonuses, but instead of the fourth, you can gain a +2 WIS bonus instead, which has more value for the pure-Defense character.