I am a VR4 rogue/assassin type NB using DW on my primary bar. My two main dps skills are Ambush (as an opener) and Surprise Attack, in addition I use skills like Killer's Blade, Swallow Soul and Blood Craze. This build is fairly reliant on critical hits, so I use daggers and medium armour, and have narrowed down my Mundus Stone choices to The Thief and The Shadow. However, here I am stuck. The Thief raises my weapon crit chance from 34% to 39% and my spell crit chance from 12% to 17% (the latter doesn't display properly, but I think it's just a visual bug). This increase seems decent enough. But how does it compare to the extra damage from The Shadow? Apart from knowing how much extra damage does it provides, it would also be useful to know whether skills like Ambush or Surprise Attack use the spell crit or weapon crit chance value, and whether spells like Swallow Soul can crit.
It would be awesome if anyone could shed some light on this matter.