I run primarily PvE and D/D. I’m running Precision > Vitality > Power > Toughness.
With Crit thief, you want to stealth and backstab until they are below 33%, then use Heartseeker. If you are having trouble with large groups, grab a Short Bow, or save up Skill Points for Dagger Storm (30 pt. Elite skill). Protip: Dagger Storm + Shadow Refuge is awesome.