However there are a lot of skills those are rarely used, ever.
I would like to share my ideas

Foul Feast (5 1 5):Blood Magic - Spell, Steal 5...25 Health from target foe for each Condition your target is suffering from (maximum 80).
Soul Bind (10 2 5): Curses - Elite Hex Spell. For 5...12 seconds, target foe "moves" 15...30% slower than normal. If that foe becomes the target of a Necromancer Hex while using a skill, that foe is knocked down.
Ulcerous Lungs (15 2 10): Curses - Hex Spell. For 10...22 seconds, target foe and all nearby foes are hexed with Ulcerous Lungs. Whenever they use a Shout or Chant or cast a spell, they begin to Bleed for 3...13 seconds.
(how can you cast a spell with Ulcerous Lungs?

Fetid Ground (10 3/4 10): Death Magic - Spell. Target foe is struck for 15...55 cold damage. If that foe is knocked down, that foe suffers deep wound for 5...17 seconds.
Armor of Unfeeling (10 1 20) Spawning Power - Enchantment Spell. For 10...30 seconds, you have 1...8 base damage reduction if you are within earshot of a spirit.
... to be continued (something like Supportive Spirit ... anyone?)
all numbers are just for reference.