DEX-based TWF Assassin builds are also pretty straight-forward. Mine is very similar to slarden's
halfling DEX build.
This build is for those without Harper:
Code:
SDK Assassin
Rogue 20
True Neutral Shadar-kai
Stats
28pt 32pt Level Up
---- ---- --------
Strength 8 8 4: DEX
Dexterity 20 20 8: DEX
Constitution 14 16 12: DEX
Intelligence 14 14 16: DEX
Wisdom 8 8 20: DEX
Charisma 6 6 24: DEX
28: DEX
Skills
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
------------------------------------------------------------
Disable 4 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 23
Open Lo 4 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 23
Search 4 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 23
Spot 4 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 23
Bluff 4 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 23
Hide 4 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 23
Move Si 4 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 23
Tumble 3 2 2 2 2 2 2 2 2 2 2 23
UMD 4 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 23
Concent 2 1 1 1 1 1 1 1 1 1 11
Balance 1 1
------------------------------------------------------------
40 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10
Feats
1 : Two Weapon Fighting
3 : Precision
6 : Dodge
9 : Improved Two Weapon Fighting
10 Rogue : Improved Evasion
12 : Improved Critical: Piercing
13 Rogue : Defensive Roll
15 : Greater Two Weapon Fighting
16 Rogue : Opportunist
18 : Quick Draw OR Mobility
19 Rogue : Crippling Strike OR Skill Mastery
21 Epic : Overwhelming Critical
24 Epic : Improved Sneak Attack
26 Destiny: Perfect Two Weapon Fighting
27 Epic : Epic Damage Reduction
28 Destiny: Elusive Target OR First Blood
29 Destiny: Embodiment of Order OR Deific Warding
30 Epic : Watchful Eye
30 Legend : Scion of: Ethereal Plane
Enhancements (80 AP)
Assassin (42 AP)
- Knife in the Darkness, Dagger in the Back, Assassin's Trick, Nimbleness, Lethality, Deadly Shadow
- Poison Strikes: Heartseeker, Sneak Attack Training, Stealthy III
- Venomed Blades III, Sneak Attack Training
- Critical Mastery III, Sneak Attack Training
- Execute, Killer III, Weakening Strikes, Sneak Attack Training
- Assassinate, Measure the Foe III, Deadly Strikes, Knife Specialization, Light Armor Mastery II
Thief-Acrobat (27 AP)
- Staff Control, Stick Fighting, Tumbler, Kip Up
- Sly Flourish III, Fast Movement
- Subtlety III, Haste Boost III
- Shadow Dodge III
- Improved Defensive Roll III, No Mercy III
Shadar-kai (11 AP)
- Shadar-kai Grit, Dexterity, Shadow Phase, Shadow Jaunt
- (none)
- Improved Dodge II, Guile
- Guile
Leveling Guide
- Ass0 Knife in the Darkness; Ass1 Poison Strikes: Heartseeker
- Ass1 Sneak Attack Training; Ass2 Sneak Attack Training; Ass2 Venomed Blades I
- Ass2 Venomed Blades II, III; Ass0 Dagger in the Back
- Ass3 Sneak Attack Training; Ass3 Critical Mastery I, II, III
- Ass1 Stealthy I, II, III; TA0 Staff Control
- TA1 Fast Movement; Ass0 Assassin's Trick; Ass4 Killer I
- Ass4 Killer II, III; Ass4 Execute
- Ass4 Weakening Strikes; Ass4 Sneak Attack Training
- TA1 Sly Flourish I, II; TA2 Haste Boost I, II
- TA2 Haste Boost III; TA2 Subtlety I, II
- TA3 Shadow Dodge I, II
- TA3 Shadow Dodge III; Ass0 Nimbleness; Ass5 Knife Specialization
- Ass5 Measure the Foe I, II, III; Ass5 Assassinate
- Ass5 Deadly Strikes; TA2 Subtlety III; TA1 Sly Flourish III
- TA0 Stick Fighting; TA0 Tumbler; Ass5 Light Armor Mastery I, II
- TA0 Kip Up; TA4 Improved Defensive Roll I, II, III
- SK0 Shadar-kai Grit; SK0 Dexterity; TA4 No Mercy I
- Ass0 Lethality; TA4 No Mercy II, III
- SK0 Shadow Phase; SK0 Shadow Jaunt; SK2 Improved Dodge I
- SK2 Improved Dodge II; SK2 Guile; SK3 Guile; Ass0 Deadly Shadow
Destiny (24 AP)
Shadowdancer
- Stealthy III, Technician I
- Lithe III, Skill Mastery
- Shrouding Strike III, Meld into Darkness I, Grim Precision III
- Improved Invisibility I
- Untouchable, Executioner's Strike I, Sealed Soul
- Shadow Form, Dark Imbuement
Twists of Fate (14 fate points)
- Balanced Attacks (Tier 3 Primal)
- Hail of Blows (Tier 2 Flowers)
- Rejuvenation Cocoon (Tier 1 Primal)
Skills: UMD and trap skills are the must-haves, of course. Hide is maxed largely to max out extra sneak atks from Scion of Ethereal Plane; in which case, might as well max Move Silently too. I like having Concentration on my UMD toons, even though it's a cross-class skill. Why max Tumble? Because
backflips FTW! 
But you could take Diplomacy, Haggle, or Heal (more Pos Spellpower for Cocoon).
Optional feats: Dodge for the extra Dodge bonus (duh) and Epic DR for moar DR (also duh) are pretty good options for lvl 6 & 27 feats, IMO. Then it's mostly a question of whether you want more DPS or more survivability: so either Mobility (+2 Dodge & MDB) or Quick Draw (slightly reduces the delay on using action boosts for a little more burst DPS) at lvl 18; either Elusive Target (extra 5% miss chance) or First Blood for a bit more DPS at lvl 28; and either Deific Warding for extra PRR/MRR or Embodiment of Order for more DPS at lvl 29.
Enhancements: obviously Assassin is the primary one, but Acrobat has lots of useful goodies too - Fast Movement, Shadow Dodge, Haste Boost, Imp Defensive Roll, No Mercy, Kip Up (knockdown immunity). SDK Shadow Jaunt is cool: works like Abundant Step / Leap of Faith. Leftover APs went towards Imp Dodge and SDK Guile for an extra +2d6 SA. If you feel your trap skills need improvement, shift APs from SDK and/or Acrobat into Mechanic.
Sneak attacks (SA): 10d6 rogue levels + 8d6 Assassin + 2d6 SDK + 3d6 Imp Sneak Atk feat + 6d6 Shadowdancer = 29d6 SA (101.5 avg dmg per hit). I believe you can get another +22 SA from gear. I've seen posters claim endgame Hide skills of 150-ish, which means +50 SA from Scion of Ethereal Plane; but we're talking fully tricked out gear, tomes, etc. But I'd guesstimate even a first-lifer with more modest gear will hit Hide 90+, so that's still means 30-plus SA bonus. So you're talking somewhere in the neighborhood of 150 to 180 pts of SA dmg per hit by endgame and that's before you factor in 150% Melee Power scaling.
Required extra gear to start:
- None, though a lot more healing potions certainly wouldn't go amiss...

Recommended extra gear to start:
- +6 INT swap item for trapping. Until then, you can use Fox's Cunning potions.
- Deadly & Seeker items: helm and goggles can be used as swap slots.
- Deception gear: Backstabber's Gloves are the obvious choice, though it means giving up your initial doublestrike bonus. At lvl 17, Golden Guile is a good option, since it also adds Dusk and boosts your Bluff & Diplomacy.