It's a good start to a tournament list, it just needs optimising.

HQ:
Your overlord should be loaded out with sempiternal weave, mindshackle scarabs and warscythe. This will make him a beast in challenges, also he can tank some wounds with his 2+ save, this load out comes in at 130pts.

The only time you need to bring a harbringer of despair is with deathmarks, but you shouldn't need to bring any at 1000pts, so id say remove him and free up points.

Troops:
If you're going to put your warriors in night scythes then 5 man squads is enough, but if you wanted ghost arks then 10 is the correct number, adjusting squad sizes to account for characters and the ghost arks capacity.

Fast attack:
3 lonely wraiths won't be that much of a threat, and if you can't hide them well, then it's also an easy first blood. My advice is to either remove the entire unit, or beef it out to a 6 man unit, but definitely get rid of all whip coils, not necessary.

Heavy support:
2 annihilation barges is okay, but with the saved points I think 3rd is an excellent choice . Nonetheless annihilation barges are an excellent choice, probably still one of the most cost effective units in the game.

I hope this helps

minimanj