Poison Dagger can be extremely deadly should you focus on it. The Poison Dagger Spell is designed to offer Necromancers the option to effectively use another weapon type should he choose that path to follow. There are some rare, high-level, Necromancer oriented daggers in the game that will be desired by any poisonous player.
The apothecary skills of the Necromancer lay fundamentally in the studies of venoms, toxins and other poisonous substances. Not only can a skilled Necromancer identify the various strains of poison that he might come across, but he also maintains a ready supply of samples. Rarely does he shy from their use. In a common application of this skill, the Necromancer paints his dagger with a thin coat of virulent poison. The greater his ability, the more potent the poison.
↑Diablo II Manual, page 73. Blizzard Entertainment, 2000.