The Rogue|Assassin + Warlock is intriguing. It has oodles of flavor!
Here's my modified version at level 4 with a purchased level 1 weapon and level 3, 4 and 5 magical items. Also purchased lots of stuff to augment a master of disguise and deception theme.
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====== Created Using Wizards of the Coast D&D Character Builder ======
Vir, level 4
Human, Rogue|Assassin
Hybrid Assassin: Hybrid Assassin Fortitude
Pact Initiate: Pact Initiate (fey pact)
Hybrid Talent: Shadow Step
Versatile Expertise: Versatile Expertise (Heavy Blade)
Versatile Expertise: Versatile Expertise (Light Blade)
Background: Birth - Cursed (+2 to Bluff)
FINAL ABILITY SCORES
Str 8, Con 14, Dex 19, Int 13, Wis 10, Cha 15.
STARTING ABILITY SCORES
Str 8, Con 14, Dex 16, Int 13, Wis 10, Cha 14.
AC: 19 Fort: 17 Reflex: 19 Will: 16
HP: 37 Surges: 8 Surge Value: 9
TRAINED SKILLS
Endurance +9, Thievery +11, Streetwise +9, Stealth +11, Acrobatics +11, Bluff +11, Intimidate +9, Arcana +8
UNTRAINED SKILLS
Diplomacy +4, Dungeoneering +2, Heal +2, History +3, Insight +2, Nature +2, Perception +2, Religion +3, Athletics +1
FEATS
Human: Hybrid Talent
Level 1: Pact Initiate
Level 2: Versatile Expertise
Level 4: Cursed Shadow
POWERS
Bonus At-Will Power: Duelist's Flurry
Hybrid at-will 1: Piercing Strike
Hybrid at-will 1: Executioner's Noose
Hybrid encounter 1: Gloom Thief
Hybrid daily 1: Targeted for Death
Hybrid utility 2: Fast Hands
Hybrid encounter 3: Low Slash
ITEMS
Challenge-Seeking Short sword +1, Deathcut Leather Armor +1, Gloaming Shroud +1, Hedge Wizard's Gloves (heroic tier), Accurate dagger, Adventurer's Kit, Candle (10), Disguise Kit, Fine Clothing, Camouflaged Clothing, Bottle of Wine, Footpads, Grappling Hook, Holy Symbol, Thieves' Tools
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It also alleviates the difficulty Assassins have going nova for a round by opening up the Rogue minor action Low Slash and the daily that knocks prone.
Add 8 trained skill (2 of them social, 1 knowledge) and you've got a very versatile character both in and out of combat.
Round 3 Nova at level 5:
Round 1, spot the BBEG and Target for Death (3d8+4) then double shroud BBEG
Round 2, close on BBEG, strike and position with Duelists Flurry (4+2d6 Sneak Attack) then double shroud BBEG
Round 3, apply the hurt
- Invoke 4 shrounds (free action)
- Gloom Thief 2d6+5+4d6 (or 3d6 on miss) and become invisible to target (standard action)
- Action Point
- Walking Wounded 2d6+5 and knock target prone (standard action)
- Low Slash 1d6+5 (minor action)
- Sneak Attack 2d6 (if either Low Slash or Walking Wounded connect)
- Shadow Step if you can or Shift and roll stealth if Gloom Thief connected
I'm not savvy enough to figure out the average damage but you've got CA on Low slash if Gloom Thief or Walking Wounded hits so the numbers are in your favor. In addition to that you've got 3 of 5 attacks against NADs, and two of those are melee weapon attacks with +11 to hit.
I realize this is not the end all be all build for damage. I'd play it though just for the number of other skills and fun things this Assassin|Rouge+Warlock can do.