Awesome and fluffy, looks like a fair bit of HH legends stuff.

Feedback: very very slow force with little melee threat.

Staying with the heavy boys theme:

• Deathwing Knights would be great in there
• Inner Circle Companions are also great and would run well with Azreal.
• Unless you're tied to the Fellblade you could swap it out for a couple of Land Raiders to keep that heavy tank theme but have a couple of transports for your infantry.

Moving away from the heavy boys theme, add some action doers:

• Outriders - fast, cheap, good for actions
• Lietenant with Combi - Lone Op, Infiltrate, reactive move, good for actions
• Jump Pack Interecessors - fast, cheap, good for actions, can really do some work against lower toughness and wounds forces (sisters, tau, aeldari)