Here is a Dragon Age Inquisition Dual Dagger Assassin Rogue Build Guide written by KineticGTR.
One of the most complicated and rewarding classes to play in Dragon Age Inquisition, a dual dagger Assassin Rogue! Timing, position, and resource management make playing this class a test of focus more than any other I've played.
This guide focuses on how to build your class using a combination of standard skills from the Subterfuge, Sabotage, and Double Dagger skill trees, and new active and passives from the Assassin specialization tree for Rogue.
This build has been put together from a fresh respec. With about 15-20 points to place, you can put together a very powerful Assassin that has everything it needs to dominate on the battlefield.
Twin Fangs /
Ripping Fangs (Skill upgrade) /
Flank Attack /
Skirmisher (Skill upgrade) /
Dance of Death /
Sneak Attack /
Caltrops (unused, but necessary) to get to the passive Looked Like It Hurt
Lost in the Shadows (Optional skill upgrade) /
Shadow Strike /
Quick Blade (Skill upgrade)
Hidden Blades /
Overkill (Skill upgrade) /
I Was Never Here /
Knife in the Shadows /
Mark of Death /
Here are some other skills worth investing in and replacing Evade with.
Hook and Tackle - A great skill that can help you reach archers and mages on the outer edges of battle. And with it's upgrade It Beats Walking, it costs no stamina and has no cooldown.
Knockout Powder/Knockout Bomb, and the passive Mercy Killing could also be worth taking and applied in certain situations. You will automatically critical hit a target this way.
Poisoned Weapons and it's upgrade Infected Wounds. A decent damage builder, but with you other skills, your target is most likely dead way before the poison even works its duration.
Gameplay: There are basically two plans of attack that I use and I'm almost always positioned if possible behind my target(s)
Method 1 for normal encounters, single or multiple targets - Stealth, move behind target, Hidden Blades, Flank attack for Stealth, Shadow Strike, Stealth, Twin Fangs. At this point, something is probably dead. If not, Deathblow. Now it's definitely dead. ;)
Method 2, recommended for targets with high HP - Mark of Death, Flank Attack for Stealth, Hidden Blades, Stealth, Shadow Strike, if enemy is 25% health or less, trigger Mark of Death. If not, consider Twin Fangs and/or Deathblow, then Mark of Death. Probably dead. ;)
For extremely high HP enemies (ex: dragons) your priority skills are Mark of Death, Hidden Blades, Flank Attack, Twin Fangs, Shadow Strike (to reduce cooldowns of previous skills) When enemy drops below 50% health, start using Deathblow.
As many chances as you get, attack from Stealth. HOWEVER! Do not stand around doing nothing, waiting for Stealth to attack. If you're waiting for Stealth, and/or low on stamina, use basic attacks. You should always be attacking or moving into position to attack from behind!
Also, unless you have aggro, don't go into Stealth and then wait more than 2-3 seconds to use a skill. Instead, use basic attacks, and when you're skills are off cooldown, then go into Stealth and attack with Skills.