Probably Dual Blades, since their Life Drain skill isn't too great nor does it activate often, and it allows them to solo PB statues.

NlL's need it the most because they have the worst defense, have to spam 100's of pots just to train

Shad or DB. It helps at times during gollux.

omg mixed opinions... and since i already have a high level db, this is between shad and nl so which one? more suggestions pls

i would say NL since they're more squishy

I would say Night Lord as well since we are naturally squishy.

Why not all the thieves...lol

NL... no natural Evade or Damage Reduction to speak of. We only have that 47% avoid chance DB and Shads have and our natural avoid.

NL's in general need it the most because they have zero Evasion Rate (this is different from Dodge Rate), and Damage Reduction.
DB's have 70% Evasion Rate, and 20% Damage Reduction with Mirrored Target active.
Shad's have 20% Evasion Rate, and 60% Damage Reduction.

It also depends on the boss. Vampire would be best suited for a Shad at Gollux because they have close range attacks. DB's can move with Bloody Storm, and NL's can stay ranged, or move in the opposite direction of where he's facing on Hell Mode to avoid his breath at the Jaw. At bosses without % HP attacks, Shad's can tank the damage, and DB's can evade it altogether, leaving NL's to rely on their natural Avoid and 45% Dodge Rate.

Nlight Lords hands down. Without any hp additions we have the lowest survival rate. And even with additions, we still have the lowest survival rate because we have a higher chance of getting hit and get hit for the most damage. It's hard to use drain when you die in one hit.