Secondary professions for a Necromancer

Necromancer Warrior
This profession combination provides little benefit for a Necromancer primary, however shields can provide extra armor, and Mark of Pain, Barbs and Flurry can be combined to increase damage.

Skills from the Tactics line such as "Shields Up!" can help the Necromancer and his teammates.

Necromancer Ranger
Serpent's Quickness can accelerate slow recharging spells.

Necromancer Elementalist
Glyph of Lesser Energy can be used for energy management.

Necromancer Mesmer
Skills such as Wastrel's Worry can be combined with a Necromancer's shutdown skills such as Spiteful Spirit.

Skills in the Inspiration line such as Power Drain can be used for energy management.

Mesmer interrupts such as Web of Disruption can be used to counter enemy skills.

Necromancer Monk
Healing Prayers can counteract sacrifices from skills like Order of Pain to enhance their damage output.

Soul Reaping is often used to fuel the more expensive healing or protection skills from the monk lines

Spoil Victor is a powerful elite for a 55 hp Necromancer

Necromancer Assassin
Skills such as Viper's Defense and Dark Escape can be used as defensive measures for a Necromancer. Deadly Arts hexes such as Enduring Toxin can be combined with a Necromancer's degen hexes.

Necromancer Ritualist
A Necromancer spirit spammer rarely has to worry about running out of energy.

Necromancer teleports, unlike shadow stepping, allows one to carry bundles with them. A N/Rt can be a melee bomber by teleporting into a clump of foes and dropping an item.

Necromancer Paragon
Many Command skills can affect minions, and Leader's Comfort can be an effective self-heal without Leadership when surrounded by minions.

Necromancer Dervish
Defensive skills such as Armor of Sanctity + Veil of Thorns can be used to increase a Necromancer's survivability. Vital Boon + Signet of Pious Light can be used as a powerful self heal.