One of the best ways for rangers to kill necros is to use Broad Headed Arrow and apply poison, then just stick in Diablating Shot to get rid of their energy and you have one unhappy (and most likely dead) necro.
My name: Caleb Schatzman
ToJ name: Thi3rd
Main Character Name: Third Blessing (Dervish)
Other chars: Third Vindiction (Warrior) Third Lamentation (Assassin) Third Angel (Monk) Andalui Ven (Mesmer) Van Of The Abyss (Ritualist) Skies over Calvery (Ranger)