Need help on my Necro

I'm currently trying on a N/W build

Blood 15
Death 16
Axe 2
Tatics 2

Axe: enchancement last 20% longer, lengthen duration on cripple
Shield: +45hp dmg, reduction

Dark Pact - Spell 2 secs recast
Sacrifice up to 10% Health and deal 48 shadow damage to target foe

Touch of Agony - Skill 3 secs recast
Sacrifice 10% of maximum health. Target touched foe takes 58 shadow damage.

Dark Aura - Enchantment Spell
For 36 seconds, whenever target ally sacrifices Health, Dark Aura deals 53 shadow damage to adjacent enemies, and you lose 21 Health.

Blood Renewal - Enchantment Spell
Sacrifice 33% maximum health. For 10 seconds, you gain health regeneration of 6. When Blood Renewal ends, you gain 190 health.

Aura of the Lich {Elite} - Enchantment Spell
For 75 seconds, your maximum health is halved, but you take half damage and half healing from all sources. When Aura of the Lich ends you're healed for 240 health.

Life Siphon - Hex Spell
For 23 seconds, target suffers health degeneration of 3, and you gain health regeneration of 3.

Death Nova - Enchantment Spell
For 36 seconds, if target ally dies, all nearby foes take 105 damage and are Poisoned for 15 seconds

Res Sig

This build requires Dark Aura to Sacrifice. Each time when i use Dark Pact i deal 53 aoe dmg + 48 dmg and each time when i use Touch of Agony i deal 53 aoe dmg + 58 dmg, all of these dmg deal shadow dmg and ignore armor. i can continuously spam both Dark Pact and Touch of Agony none stop to drop my target quickly.

The dmg out put is increadbly high, but the problem i have is my servival ability even with my shield. I do not have problem on sacrificing health, My problem is when ppl target me and trying to kill me. I've try something to make me servive longer such as Arua of the Lich. My max health is halved, I take half dmg and half healing from all sources, but i gained double effect on regenations. But still, i have problem on servive.

Any idea to make me servive longer?