I fear your list lacks killing power. It really only has the Immortals that do any decent shooting. Once those are gone or locked in combat, it's kinda over.
No need for that many scarabs I'd say. Nothing important to bubble wrap and at a total of 1000 points you won't get anything too serious deepstruck against you.
I'd definetly pump the number of warriors or Immortals up.
Here's my recommended list:
HQ: Illuminor Szeras (Warlord, warlord trait: +1 LD 6")
Overlord /w Void Blade (relic: Veil of Darkness)
10x immortals /w Telsa Carbines
C'tan shard of the Nightbringer.
There. Everything in this list is dangerous. The Immortals /w MWBD, the Warriors upgraded by Szeras and of course the C'tan shard.