This has been my preferred build for months for various reasons. First of all i play in a guild with great maintanks (and if i were to maintank, i would probably use the 31 x x build), so most of this post revolves around being a node guarder in ranked wzs, or an offtank.
So for starters, force in balance is by far the best cap stopper in the game, and does great damage used solely as an AoE even with the 39 force cost - just save it for when you can hit more than one target. The extra damage on double strike is a no brainer, it makes this build amazing for node guarding and solo 1v1 it can usually always beat a 31 x x build.
Some might argue having instant force lift is superior alongside 1 point in backstab - this is IMO a weakness - the 23 x x builds are almost all weapon damage. if a class hits you with say, a 30% accuracy debuff then pops their cooldowns which increase their defense - gg hitting them and proccing particle accel for projects OR using your backstab proc - and not only that these projects are never building towards the harnessed shadows attack, which still provides a useful heal and great dps with force potency.
If i come up against another shadow who uses say, Deflection (+50% melee defense for 12s), all i have to do is cycle project into tk throws for very reasonable dps (1 stack tk throw with no intterupt or pushback, 25% bonus damage). It allows this build to adapt to any given situation, regardless of what defensive cooldowns the opponent uses. Another boon of being able to project into 1 stack tk throw you've now got the ability to kite sentinels and heavy melee builds without having to charge in and DS, DS, project, backstab etc.
