-----For Reference-----
The main problem I had with the Night Lords in Traitor Legions is that their main shtick, the lowering of leadership to force fear/leadership failure, is just so situational and largely useless. It has a lot of luck behind it working in your favor, half of the effect is completely ineffective against any
SM army, and the armies which lack a lot of fearless options (Eldar/Tau) are typically geared to blast you off the board before you ever have a chance to get into combat...and IF you do manage to get into combat, and they DO happen to fail, then whoop-dee-do, they hit on 5's. I so wish Night Lords got a better set of rules, but I digress. /endrant
I do agree with you 100%, Night Lords look freaking amazing. To this day, one of my favorite paint schemes comes from the way Night Lords were painted in the 3.5 Codex; it's just everything that is chaos in the best way.
As for the list, it's an 1850 game. My rule of thumb is that for every 1000 points, you can bring 1 big baddie of some type (single big ass monster, awesome
HQ choice, specific unit of death, etc.), and build the rest of your army around that. 1850 has become a nice standard, and while it's "basically 2000 points", don't be fooled...it is not. You can sometimes get away with two big baddies in an 1850, but there needs to be a lot of synergy in the army to justify the heavy point sink. As it is, you have 3 big baddies, and they don't really have a lot of synergy either together or with the rest of the force. This is from both a "fun to play" and "competitive" viewpoint.
Based on your initial post, it sounds like you intend to have a highly mobile strike force; lots of hunting things. I kept that in mind when going through your list.
First, the basics. Your points are incorrect; you list 1850, but you're actually at 1820. I believe you forgot that the Lord in the Raptor Talon gets his jump pack for free, but I'm not sure where the other 15 points came from. Is there a piece of equipment or upgrade you forgot to list? In either case, you did not list equipment for your Cultists (I assumed standard bolt pistol/close combat weapon) or for your Heldrakes (I assumed the baleflamer would be taken). Lastly, who are you making your Warlord, the Lord or the Daemon Prince? Which Warlord Traits are you rolling on?
Second, the recommended alterations.
1. Drop the Heldrakes down to 2, keep the baleflamer on both and see how you like it, but consider taking the autocannons.
GW box-art aside, don't expect your heldrakes to be vector striking planes out of the sky. You are entirely lacking in anti-air, and considering the bulk of your force is scheduled for a close combat rendezvous, you're likely to find your Heldrakes are without viable targets by the mid game. Give them the autocannons, though, and now you have some excellent air superiority that can better aid your ground troops in the mid-late game.
2. Keep the Chaos Knight, as it is a good choice for Night Lords. The range isn't great, but that thermal cannon will work wonders. Go ahead and give it a dirge caster; with the size of the Knights' base, that can become an 18" bubble of no-overwatch, a great boon to an assault oriented army, and at a meager point cost. Also, while you can't take a mark on the Knight, you can take a Legacy of Ruin. Veteran of Scouring will give you
IWND and Hatred(
SM's), both of which are freaking awesome, but it is the most expensive at 40 points. Maelstrom Raider would fit the Night Lords bill really well (an outflanking Knight is nothing to sneeze at), and Fourth Quadrant Rebellion will turn those taxing Cultists into a couple units of fearless bubble-wrap if you wanted (and gives you a 4++ right before it bites the big one). Definitely take one, up to you which you think is best.
3. On the Daemon Prince, if his sole purpose is going to be flying about and shrieking at the world (LOVE THIS IMAGE, PLEASE MAKE A BANSHEE DAEMON PRINCE), then he is well kited out to do so. Stormplate is a good choice, as that will stack to give you a 2+ re-rollable cover save when jinking; for when your 2+ re-rollable armour save fails? A damn deadly machine as long as it stays in the air, and doesn't perils to death. You won't have a ton of warp charges to play with, so expect being heavily shut-down by even mediocre psychic lists, and don't expect to ever get a shriek off against a psychic heavy army/list. Yeah it's only 1 warp charge, but if your opponent figures out that you're lowering his/her leadership in preparation for a shriek, be prepared to have them throw all their dice to stop it.
4. Lord. In keeping with your theme of lowering the leadership of your enemies to scare the pants off them and shriek them away, how can you NOT give this guy the Vox Daemonicus?! It even messes with your enemies reserve rolls. Don't think, just add it. If you are planning on running him with the Warp Talons, you need to beef up their numbers. You can't take marks to make them tougher or better killers, so you'll have to do it with numbers. I do not normally advocate taking Warp Talons to begin with, as they are expensive (both the physical models and the game points), and they leave a lot to be desired. However, as they are intended to be run here, their problems are largely gone. They'll be fearless while the Lord is with them, so no getting shot and fleeing from a failed morale check. They'll be able to charge on the same turn they arrive, so no waiting for a full round of shooting to sweep them before they can rip and tear. The Lord provides them with assault grenades (WHY DONT THEY HAVE THESE FFS!), so they won't be at initiative 1 when making the vast majority of their charges. Their first charge will be disordered, so no bonus attacks for charging, but you will still pump out 19 attacks from just the Warp Talons (if they all survive), with lightning claws to boot, in addition to hammer of wrath attacks; a veritable meat grinder for everything save
TEQ, and even they are bound to lose a guy or two from sheer volume of attacks, AND you have a lot of fearless bodies with a 5++ that can actually take their attacks back. Your Lord is well tooled to rip and tear regulars, but he wont be able to stand up to dedicated combat characters. T4 and a 5++ without
EW just isn't going to cut it; even a standard terminator has a decent chance of insta-gibbing him. Be careful.
5. The Raptors. Honestly, they're fine, but I'd drop the combi-melta from the champions. They're going to die early, it's just the fate of chaos, and it's often before they ever get to use that shot. Don't forget that, unlike your regular Raptors, who can just take a meltagun, the champion must swap out one of his weapons to get that combi-melta, which means losing an attack. Consider just giving him melta bombs instead. More reliable, and can be used in combat; much more points efficient and effective.
6. Cultists. Body tax to get your LOW and
DP into the game, so keeping them cheap is fine. WORD OF CAUTION: the will not be getting any useful bonus for being in a Night Lord force, as they lack (and have no way of getting)
VotLW. They are, however, your only source of objective secured in the entire list, and represent over half of your body count. I think you'll find you either keep them hunkered down in cover camping an objective, in which case I'd give them each a heavy stubber so they aren't entirely useless, or bubble wrapping your Knight to prevent any would-be-shenanigans from occurring, in which case give them a flamer. This second option also pairs well when you take the Legacy which makes your cultists within 12" fearless.
-----Revised List-----
+++ Night Lords (1850pts) +++
++ CSM Night Lords Murder Talon (1040pts) ++
+ Core (700pts) +
········
Raptor Talon (700pts)
············
Chaos Lord [Aura of dark glory, Jump Pack, Lightning Claw, Power Fist, Veterans of the Long War, Vox Daemonicus, Warlord]
················
Power Armour [Frag and Krak Grenades]
············
Raptors [2x Meltagun, Veterans of the Long War]
················
4x Raptor [4x Bolt Pistol, 4x Close Combat Weapon, 4x Frag and Krak Grenades]
················
Raptor Champion [Bolt Pistol, Close Combat Weapon, Frag and Krak Grenades, Melta Bombs]
············
Raptors [2x Meltagun, Veterans of the Long War]
················
4x Raptor [4x Bolt Pistol, 4x Close Combat Weapon, 4x Frag and Krak Grenades]
················
Raptor Champion [Bolt Pistol, Close Combat Weapon, Frag and Krak Grenades, Melta Bombs]
············
Warp Talons [Veterans of the Long War, Warp Talon Champion]
················
9x Warp Talon [9x Twin Lightning Claws]
+ Auxiliary (340pts) +
········
Heldrake Terror Pack (340pts)
············
Heldrake [Hades Autocannon]
············
Heldrake [Hades Autocannon]
++ Combined Arms Detachment (810pts) ++
+ HQ (310pts) +
········
Daemon Prince (310pts) [Close Combat Weapon, Mastery Level 3, Spell familiar, Stormbolt Plate, Tzeentch, Wings]
+ Troops (110pts) +
········
Chaos Cultists (55pts) [Flamer]
············
Cultist Champion [Auto Pistol, Close Combat Weapon]
············
9x Cultists [9x Close Combat Weapon]
········
Chaos Cultists (55pts) [Flamer]
············
Cultist Champion [Auto Pistol, Close Combat Weapon]
············
9x Cultists [9x Close Combat Weapon]
+ Lord of War (390pts) +
········
[FW] Chaos Knight Errant (390pts) [Dirge Caster, Foe-reaper Chainsword, Heavy Stubber, Ion Shield, Legacy of Ruin: Fourth Quadrant Rebellion, Thermal Cannon]
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Given your desires, that's how I would run it. Again, baleflamer/autocannon is up to personal preference, and going one of each isn't the worst idea in the world either. Either the
DP or the Lord would make for a decent Warlord, but if you intend to use the Night Lords table, the Lord is a better option, as he can benefit decently from any trait, and REALLY well from some.
As I see it, your main problem is being short on bodies while also being short on resilience. You've got two planes in the skies, a single
DP flying about, 19 marines with jump packs (9 of which have no ranged attack at all), 20 piss poor excuses for anything but cannon fodder or meat shields, and a Knight. You'll have some clever tricks up your sleeve, but you'll still need to weather your opponents return fire, and you won't be showing them anything but 20 T3 cultists and (possibly) a Knight and (again, possibly) the
DP on turn 1. Night-fighting will definitely help your chances, but there's no guarantee you get the rest of your force in on turn 2, and I think any delays are REALLY going to hurt.
An overall change I would make would be to include more bodies at the expense of the Warp Talons. I'd make my
DP the Warlord, make the Lord in the Raptor Talon fill a different role besides
CC (Burning Brand comes to mind) while keeping his cost down, and throw him into a third unit of Raptors, give them flamers to compliment the Lord. With the extra points I'd add more cultist units, add in two more bare-bones Raptor units as troops in the
CAD (so 5 total Raptor units), or add one more Raptor unit (4 total Raptor units) to the Murder Talon, but give them plasmaguns to hunt elites and
MC's.
All things considered, the army would definitely look badass, is a great thematic list, and does have options available for expanding/altering as the army ages/grows; it won't be stuck as a one trick pony.
Best of luck screaming from the skies!
Cheers.
5000pts W4/ D0/ L5
5000pts W10/ D2/ L7
10,000 
40K Primaris Celestial Lions/Black Templar Crusade Plog - 
30K Night Lords & Blood Angels Plog -