Double Dragon-Cron

So, I was futzing around with some flyer based builds and I came upon this one. Seems like it would certainly rain down some damage, and with 4 scoring grot units, it could be pretty effective at keeping objectives. Thoughts?

Double Dragon-Cron (1850pts)

Chaos Space Marines (Primary Detachment) Selections:

HQ

• "Billy" - Daemon Prince - Burning Brand of Skalanthrax, Gift of mutation, Level 0, Slaanesh 
  • Wings
  • Power Armour
    
    

Troops

• 10 - Cultists - Autopistol
• 10 - Cultists - Autopistol

Fast Attack

• Heldrake - Baleflamer
  
  
• Heldrake - Baleflamer
  
  

Heavy Support

• Maulerfiend - Magma cutters (Magma Cutter)
  
  
• Maulerfiend - Magma cutters (Magma Cutter)
  
  

Necrons (Allied Detachment) Selections:

HQ

• "Jimmy" - Necron Overlord - Mindshackle Scarabs, Phase Shifter, Sempiternal Weave, Warscythe
  • Royal Court
    
    • Harbinger of Despair - Abyssal Staff (Shroud of Despair)
      
      

Elites

• 5 Deathmarks
  • Night Scythe
    
    
    

Troops

• 5 Necron Warriors
  
  • Night Scythe
  
  
• 5 Necron Warriors
  
  • Night Scythe
  
  

Heavy Support

• Doom Scythe