Well, a small thing would be to drop the Warrior squad to 8, so that everyone can embark on the GA at the same time. Otherwise, someone's slogging it on foot.
Given that most of the missions need you to claim objectives, you should probably invest in more than one troop choice. If they go down, you'll be hard pressed to win a game.
I think I'd save points on the Sempiternal Weave. You have high enough T to make Power Swords less effective than the user would like. Power Axes and Fists will push through the SW anyhow. Otherwise, the only major difference is if you're somehow caught with a Krak Missile, and even then you won't be insta-jibbed.
So that's 36 points to spread around.
If you also drop the Scarabs, you'd have enough points to buy a minimum 5 man Warrior Squad, but not enough to give them a Cryptek or Lord to make them into something with bite.
I would suggest...
100 - Overlord: Warscythe
205 - [5] Warriors:
Harbinger of the Storm,
Ghost Ark100 - [5] Warriors:
Harbinger of DestructionCDX - Annihilation Barge: Gauss Cannon [? Not my cup of tea, but maybe a better choice for AT?]
Which gives you a tiny amount of points leftover, that you probably can't spend anyhow.
You could sub out your Overlord and HoD for Illuminor Szeras instead, which would let you buy a couple more Warriors... and give a boost to one of your units.