Having used Mandrakes a couple of times recently, I would second the suggestion to split them into two smaller squads of five. They can be quite useful for getting onto objectives in the first turn, both in Eternal War and Maelstrom missions. You don't need the Nightfiend though, plus you'd have to convert one or paint one differently to remember which one he is, so I'd say save yourself some effort there.
You might find yourself slightly lacking in anti tank fire. As I'm not sure the splinter cannon Scourges would be that useful, I would consider swapping them for either another squad with haywire blasters or heat lances, or perhaps another Ravager.
Personally I don't mind your big unit of Incubi - those numbers will mean they might survive overwatch and potentially going last. I tend to have at least five with a character myself, and have found six to be a good number. You could maybe stand to lose one or two bodies to save on points, plus that unit with the Archon is a lot of points by itself.
My other car is a Ravager