Due to the recent information on Duergar in the Dhampyr article in Dragon Magazine 371, the bearded quill would not unbalanced the race if it was upgraded to 5 ongoing poison dmg and -2 attack rolls...
Quills (minor; encounter) Poison
Ranged 3; +10 vs. AC; 2d8 + 8 damage, and the target takes
ongoing 5 poison damage and a –2 penalty to attack rolls
(save ends both).
This is the power used by the:
Bloodcrazed Duergar Dhampyr Level 8 Elite Brute
Medium natural humanoid (devil, vampire)