This is what I am looking at for a solo/instance PvE build for a Sab. I specify PvE since I would spec differently for PvP (see: Infiltrator). I ran Sab in B4 and really, really enjoyed it. Setting charges and blowing them up kept a smile on my face the entire time, and the utility available to the Sab allows for some really sick kiting. Also, Time Bomb on a deer will cheer up anyone.

Looking at the build, I wanted to get as much as I could out of the main tree, but still have some points to make the other trees somewhat useful. I chose Rift as my second soul due to Shadow Swift, and after reviewing the other souls, I think it offers the best low-level bonuses with Unseen Fury, Toughened Soul, Great Fortitude and Boosted Recovery. I went Bard on the third soul for some of the passive boosts, as well as a little extra side healing.

The question is, should get Unseen Fury or Toughened Soul or try and split them. AP will boost my damage and Armor will boost survivability. Do I really need Toughened Soul since I have Anthem of Glory? Is the 30% Boosted Recovery really going to make a difference with Invigorated Soul/Motif of Regen? Should I pull back out of Bard and dump more into Rift? How important is Combat Survival in the PvE Rifts/Instances?

The reason I mention the Invig Soul is because I can throw two of those followed by a Detonate in between cycles of 5 Charges + Detonate. They won't be big heals, for sure, but I figured that would also give me a short breather on aggro, since 5+ charges can really stack up the aggro! I like Anth of Comp, but not sure how useful that will be post 20. I like Rift's Instigate +Adhesive since I can draw attention for three second against a slow moving enemy (even moreso if I stack some Trops on beforehand), giving the Tank a 3 seconds breather (which is usually more than enough).

(Of course of of this is subject to change as there will be a huge amount of tweaking and balancing over the next few months)