Most people using Shadow Arts builds – or really most thief builds in general – will place 2 points in Deadly Arts for Mug; it has very high power scaling and provides a nice little heal, which at thief baseline health, is a pretty big deal.
With HK, it’s usually more advisable to run partial or largely Valkyrie armor while retaining berserker weapons, and using a mix of Offensive ascended trinkets with the Berserker and Berserker/Valk split stats, infused all with power.
It really depends on how you play and who you’re with, though. The SA stab build is usually more of a solo-roamer one due to the heals, and is used to help mask Thief’s lack of defenses so that a thief can skirmish a little better with heavies by adding more durability. Usually Shadow Stab builds use D/P due to its substantially easier access to stealth via BP + HS and BP’s overall improved skirmishing usefulness as well as having an interrupt via Head Shot. D/D is a much more aggressive set focused on pure damage throughput with limited utility on Dancing Dagger for skirmishing.
D/D is played primarily for its burst damage throughput due to CnD’s high scaling, allowing for a Mug + CnD + Stab to deal some of the highest – in some cases arguably the highest – burst damage in the game. Because of its limited skirmishing potential, however, a lot of players prefer the “assassin” style of play – killing the target as quickly as possible and fleeing. That said, the build archetype lacks any kind of condition removal when optimized for damage outside of HiS, so it’s risky and requires a lot of knowledge on when to dodge what. With support-roles in your group, however, it can be easier to pull off and ultimately more rewarding. Below is my build, which mathematically (food is a suggestion for what I’ve found to be overall the most useful per money spent), which is the most-optimized build possible as an assassin-based D/D thief. It will take practice, though :P
(Engage from Precast BV + Assassin’s Signet + Infil Signet + Steal During CnD animation, SoS kept as a twitch blind/init regen).
http://gw2skills.net/editor/?fZAQNAoYVlsMpypNOxzJ8PNRLhs9oVv87tuPCA-TlCBABQ8AAk4EAg1+jSFAOEAZpsiRlgpopIP9AMckA0R9nAAIA3sNDA38m38m38mFCQwYA-w
