Daemon list: 1000pts
1x Bloodthirster – Death Strike, Unholy Might, Blessing of the Blood God
This guy is mega expensive for such a small game. I highly recommend that you ditch Death Strike. It may be the only ranged attack that your army has, but it's expensive and not terribly effective anyway.
3xBloodcrusher of Khorne
These are good, though I suggest putting at least one Icon in here. Bloodcrushers are quite resilient and as it stands you only have a single Icon right now which can go very poorly if you roll badly for Daemonic Assault.
Squad 1: 14x Bloodletter with Icon of Chaos
Drop a couple Bloodletters in this unit to afford the Icon in the Bloodcrusher unit (drop two since losing Death Strike on the Bloodthirster will help).
Also, as much as it pains me to say it, splitting these guys into slightly smaller units can help you out a lot in some missions.
Heavy Support: 145pts
1xDaemon Prince – Unholy Might, Iron Hide, Mark of Khorne
This guy is really expensive and I'm not confident that he'll achieve much. Perhaps swap him out for a bunch more Bloodcrushers? Just a thought.
Best of luck,