Help with stygian coal lich

i started this build because it claims to have “insane single target” but i dont see it. the damage feels awful. i must be doing something wrong so i thought i would ask for someone more experienced than me to have a look.
i am following this guide https://www.lastepochtools.com/build-guides/welcome-to-the-naughty-list---crit-stygian-coal-lich

it says for end game i should have :

  • 150 Intelligence
  • 50% spell crit
  • 300% crit multiplier
  • 150% total cast speed (+50% from gear)
  • 60% Endurance

i have 148 int., 300 crit multi 48 spell crit. why does the damage feel so low? i just started doing empowered monoliths and can barely do them. i cant imagine doing any high content with this build but others can kill uber abberoth with this. what am i missing?
https://www.lastepochtools.com/profile/lyutsifer/character/Isawthedevil

i know my gear needs upgrades but even with this gear i should have better damage

edit, how does death seal work exactly? when i press it, it barely does anything but the guide says that its the “big damage skill” nothing seems to happen when i use it except i die quite often.

You’re missing health, you have 1200 and your death seal gives lots of damage, particularly through the 165% increased damage from Corrupted Consciousness and the necrotic shred from first generating ward through the heart relic and then popping Death Seal.

For more damage, hold down rip blood and click Drain Life every half second or so; it doesn’t look much different on the screen but you’re stacking active Drain Life’s that last 5 seconds apiece.

thanks for looking. so i’m not missing anything obvious other than health ? i wonder why the build feels so meh. by lvl 85 all my other builds performed much better. and just so i’m clear do i press death seal once or press it and leave it on for a couple of seconds and press again? i tried both ways and never see any big damage

edit- the OP in that guide has 1900 life…surely the extra 700 life he has cant make that much difference?