PvE N/Me Echo SS guide
Note: This build requires Prophecies for the elite skill Spiteful Spirit (SS)

This is an excellent way to get around the Area of effect AI of enemies, as well as get the utility of Curses and mesmers.

Attribute:
12+3+1 Curses
The remaining points go into Soul Reaping and Blood magic, possibly dipping into other attributes for optional skills.

Skills:
1: Awaken the Blood
2: Arcane Echo
3: Spiteful Spirit
4: Reckless Haste (Factions only)
5: Shivers of Dread/Spinal Shivers
6: Blood Ritual/Optional
7: Desecrate Enchantments/Optional
8: Resurrection Signet

Reasoning:

Awaken the Blood:  increases damage on Spiteful Spirit

Arcane Echo: Allows more use of Spiteful Spirit

Spiteful Spirit: A hex that does damage to a group whenever the target attacks or uses a skill.  This is the source of damage in this build, as well as its namesake

Reckless Haste (Factions only): Mitigates damage dealt and increases a groups attack rate (which means more damage from Spiteful Spirit)

Shivers of Dread/Spinal Shivers: This skill will shut down many casters, as a trade for loss of skill use on your part.

Resurrection Signet: You don't want to be caught as the only one alive without it

Optional:

Blood Ritual: Makes monks and other casters happy (remove for playing with henchmen, otherwise use)

Desecrate Enchantments: This allows you to have a damage skill after you've cursed everything with Spiteful Spirit.  Most useful when you're fighting harder groups, mainly small ones.

Strip Enchantment:  Hooray enchantment removal!

Suffering: Used to cover (slow removal) of Spiteful spirit over a group of enemies.  Better if you don't have Reckless Haste

Rotting Flesh: Additional source of damage for a small investment in Death Magic.  Good for areas without enchantments (Desecrate would be better there) and hex removal (so the damage matters more)

Otherwise, look through your Necromancer and Mesmer skills in Blood Magic, Curses, Domination Magic, Inspiration Magic, Illusion Magic, and No Attribute, and find things you like. 

Gear

Armor: +1 Curses head Scar, bonus energy armor for the rest of your body.  If you have the option, please get this armor in Factions, as the less people walking around with full scar pattern armor, the better.  If you must get scar pattern, please try to make it a male without super pale skin, and use dye.  This is just for my personal aesthetics.

Runes:

Superior Curses

Minor or Major Soul Reaping

Minor, Major or Superior Blood Magic, based on how much use of Blood ritual you intend.  More use means a higher valued rune, as the lower hp will make the sacrifice easier to heal, as well as making blood ritual more effective.

Weapon/offhand/staff:

Bonuses to look for are faster cast of curses, faster recharge of curses, chance at +1 to curses, and energy.  Avoid heath if you're using a lot of Blood ritual (see above for reasoning).  Most importantly, use a weapon that does cold damage (to trigger Shivers of dread/Spinal Shivers)

Strategy:

Cast Awaken the Blood and Arcane Echo before aggroing a group.  With all henchmen, drop 1 wand attack on a target for the henchmen, then cast Spiteful Spirit on a different target, followed by the echoed Spiteful Spirit on a third target.

Spiteful Spirit should be cast on enemies in the middle of groups, with assassins, warriors, and rangers being good targets, as they will take longer to die from other sources (prolonging SS), and they often attack frequently (triggering the damage on SS).  Follow with Reckless Haste on a group of melee attackers or rangers, and then continue with SS on other targets as it and the echoed copy recharge.

Use Blood ritual when people call for it, Spinal Shivers (of Dread) on particularly dangerous casters (Remember to attack them!), and your additional skills when appropriate.

Regarding Fissures of Woe and UW farming with a 55 monk:

I have no experience with SS duo farming, as I usually play the monk.  My friend pokorourk has this to say about farming:

Attributes:
12+3+1 Curses
2+(1-3) Soul Reaping
2+(1-3) Blood Magic
12 Illusion Magic

Skills:
1: Awaken the Blood
2: Arcane Echo
3: Spiteful Spirit
4: Reckless Haste
5: Res Signet
6: Blood Ritual
7: Desecrate Enchantments/Defile Enchantments
8: Ancestor's Visage/Sympathetic Visage

Refer to the SS guide for reasoning on these skills.  Blood Ritual is a requirement here because the monk will have no energy regeneration after casting all enchantments.  Ancestor's Visage/Sympathetic Visage is required to drain Shadow Monks' and Smite Crawlers energy, as well as removing adrenaline.  All gear is the same as the regular SS build (Save runes, as attributes are more important than hp).  Your interrupt is to stop Rend Enchantments.

Strategy:

The SS necromancer has two main things to focus on in the team build:  giving the monk Blood Ritual before battle to keep his/her energy up, and dealing damage.  Cast Awaken the Blood and Arcane Echo while the monk is engaging the group.  After the monk has all of the aggro, cast SS on a target, and then cast the echoed SS on another target.  If there are healers or casters in the group of monsters, cast Ancestor's Visage/Sympathetic Visage on the 55 monk.  Cast Shivers of Dread/Spinal Shivers on any enemy that needs to be interrupted.  Desecrate Enchantments is used as an additional damage source.

Have a great time with this build!