I've started a Betrayal army and chosen to go with Death Guard. I'll be logging progress here.
My initial List:
HQ:
Praetor - Cataphractii, Power Scythe, combi-weapon
Death Shroud - command squad x4
Moritat - plasma pistols
Elites:
Legion Terminators - cataphractii x5, auto cannon, power scythe
Legion Terminators - cataphractii x5, heavy chem flamer, lightning claws, power scythe, thunder hammer
Contemptor Dreadnought - auto cannon
Troops:
Tactical squad, power scythe
Assault Squad, chem flamer, power scythe
Recon squad, sniper rifles
Support squad, chem flamers, rhino
Heavy:
Heavy Support Squad, auto cannons, augury
Medusa artillery squadron
A couple preview shots: