Assassination’s looking pretty good these days, at least from my point of view. Here are a pair of builds, one for PvE and one for PvP. Naturally some talents may change depending on your exact team, raid, preferences, etc.
For both builds…
- Daggers only
 - Slow main, fast off-hand
 - Instant poison in main, deadly in off, crippling is applied via deadly brew
 - Wpn DPS > Agility > Mastery/Haste/Expertise > Crit
 
Level 85 Assassination Rogue DPS Build (31/2/8)
This build is aimed at maximum DPS, not max suvivability.
Assassination (31 Points)
- Coup de Grace – Rank 3/3
 - Lethality – Rank 3/3
 - Ruthlessness – Rank 3/3
 - Quickening – Rank 2/2
 - Puncturing Wounds – Rank 3/3
 - Deadly Brew – Rank 1/2
 - Cold Blood – Rank 1/1
 - Vile Poisons – Rank 3/3
 - Seal Fate – Rank 2/2
 - Murderous Intent – Rank 2/2
 - Overkill – Rank 1/1
 - Master Poisoner – Rank 1/1
 - Cut to the Chase – Rank 3/3
 - Venomous Wounds – Rank 2/2
 - Vendetta – Rank 1/1
 
Combat (2 Points)
- Precision – Rank 2/3
 
Subtlety (8 Points)
- Nightstalker – Rank 2/2 – In theory this will allow for more “attack from stealth” situations.
 - Relentless Strikes – Rank 3/3
 - Opportunity – Rank 3/3
 
Glyphs
- Prime – Glyph of Mutilate
 - Prime – Glyph of Rupture
 - Prime – Glyph of Backstab
 - Major – Glyph of Tricks of the Trade
 - Major – Glyph of Feint
 - Major – Glyph of Sprint
 - Minor – Glyph of Safe Fall
 
Level 85 Assassination Rogue PvP build (32/2/7)
Think of this build as a starting point and adjust to fit your game. For example, if Improved Expose Armor doesn’t work for you then change it.
Assassination (32 Points)
- Coup de Grace – Rank 3/3
 - Lethality – Rank 3/3
 - Ruthlessness – Rank 3/3
 - Quickening – Rank 2/2
 - Puncturing Wounds – Rank 3/3
 - Deadly Brew – Rank 2/2
 - Cold Blood – Rank 1/1
 - Vile Poisons – Rank 3/3
 - Seal Fate – Rank 2/2
 - Overkill – Rank 1/1
 - Master Poisoner – Rank 1/1
 - Improved Expose Armor – Rank 2/2
 - Cut to the Chase – Rank 3/3
 - Venomous Wounds – Rank 2/2
 - Vendetta – Rank 1/1
 
Combat (2 Points)
- 1. Improved Recuperate – Rank 2/2
 
Subtlety (7 Points)
- Nightstalker – Rank 2/2
 - Relentless Strikes – Rank 3/3
 - Opportunity – Rank 2/3
 
Glyphs
- Prime – Glyph of Mutilate
 - Prime – Glyph of Rupture
 - Prime – Glyph of Vendetta
 - Major – Glyph of Blind
 - Major – Glyph of Kick
 - Major – Glyph of Garrote
 - Minor – Glyph of Distract
 - Minor – Glyph of Poisons
 - Minor – Glyph of Safe Fall
 
More details here: Assassination Rogue Guide