Quoting not quite in order because I'm replying in a feverish haze as I see units and thoughts occur to me.
Consider chopping the "drama mask" hand off of one of these to stick a book in her hand: you should be fielding a Herald with Grimoire pretty often.
Herald of Slaanesh on steed
. Give a Greater Reward for a Greater Etherblade, plus Beguilement, and you can outflank-with-acute-senses a Daemonette squad that will always be rerolling to hit; assassinating characters in combat; etc.
Looks like somebody was playing Screamerstar before they sold you this list...
Oh man, this guy got great with psychic test changes in 7e. Any doubles within 12" is a perils? Don't have to tell me twice! People tend to autopilot put him into Hound squads, which I disagree with. Throw him in Bloodletters, where his DTW bonus matters! And who he can Scout 6" closer to the enemy, so that with a Banner of Blood, can almost certainly get an assault off against the enemy T2! And whose banner can serve as a no-scatter zone to bring in Skarbrand!
That... might be one of my favorite synergies in the Daemons book, there, so long as you have a Grimoire or Invisibility to make Skarbrand tough enough to survive the enemy shooting the turn after he comes in. And, well, a bunch of high-Initiative Slaaneshi units in his rage-bubble getting the assault and getting to strike first the turn that he comes in, for Hatred-Rage I5 attacks everywhere.
You might field 3 of these, if you want to assault a unit in cover with another unit and need to strike simultaneously, and also want to soak up enemy Overwatch? More likely just summonable material for Incursion.
plus extra disk, juggernaught
Oooh, stick 2 Horrors on the disc to be Blue Scribes and one Skulltaker on the Jugger, then. I would basically only consider fielding Skulltaker on a Juggernaut--otherwise, not enough return on his Eternal Warrior on a 2 wound mini (lack of AP2 being his only downside compared to the many upsides vs a normal Kherald on Juggernaut with Greater Etherblade). The Blue Scribes, though, with this edition's psychic tests, and rolling on Daemonology? Free WC3 powers, no test required (though perhaps a Fateweaver reroll so as not to be stuck with the heavy flamer)? Yes please!
...speaking of which, you're gonna have to get or convert yourself* a Fateweaver. That Warlord Trait, plus a reroll of a D6 per turn, is invaluable. Or, well, definitely worth 300 points, then. As for what he does... he's kind of limited to a Bolt of Change beam wreaking havoc across the board while swooping, but the rerolls are what you take him for.
Not enough. More. You want at least 20 or 30, for ideal list-building purposes. I mean, I could understand saying "I have enough minis and want to play with what I have," but... if you want to bring this unit (and T1 assaults are great, after scouting if you go second, so who wouldn't?) you need more of these guys. They also make a great retinue for a JuggerHerald with a Greater Reward and Abjuration (yaaay, 3+ Deny the Witch!) or a JuggerSkulltaker.
Ok, you only need 15 or 20 max for one squad, because while these guys are cheap and fast and killy... they are just as fragile as Daemonettes, and so opponents tend to focus-fire them like nothing else. They need some more bodies and
to have Grimoire or Invisibility thrown on them to have a good chance of reaching the enemy more or less intact.
Can also Outflank with that unit of Daemonettes led by a Herald on a Steed for a serious Outflanking contingent. Show up T2, let the enemy shoot for a turn, then assault on T3 for all you got.
Ahem. Soul Grinders are dead tough, this edition. Basically the only thing that can sneer in their direction is an Imperial Knight, with his D-weapon CC attacks and chance to auto-Explode any tank with Stomps. AV 13, 4 HP, and a good shot at a 2+ cover save? Yes please!
Speaking of which, very much consider how you're going to take on Imperial Knights. A squad of 20 Plaguebearers with Invisiblity and Prescience cast on them to tarpit it and touch-of-rust it to death? An Armorbane S7 fellow like Be'lakor or Skarbrand o get in there and tear things up? Screamers with their S5 Armorbane trying to get through AV13 (don't count on it)? Warp Gaze from a Soul Grinder (with Prescience, to have a good shot at hitting) pincered with D3 S9 shots from a Burning Chariot, to force the Ion Shield invuln to only be able to protect against one of those? You have to burn through a potential 6 AV 13 4+ invuln hull points, so... you'd better have a game plan or else a Knight will wreck your army (and your day), now that you no longer have access to a melta-spam army.
3 Nurglings are the new Cultists--a few points cheaper and essentially Fearless, to boot! Good that you have those.
Definitely consider building and painting that unbuilt DP as Be'lakor. Or Skarbrand. My whole game-plan for Daemons these days is basically to field 2 out of 3 of the following: Be'lakor, Fateweaver, and/or Skarbrand, then building the rest of the list to synergize around those characters. Unfortunate, then, that you don't have any of the 3 best characters in the Daemons book...
It's late/early enough that I can definitely tell that I'm in the manic state of fatigue (generally hits me around 2:30 am--well, would you look at the time), so as much fun as I am having with this random scattershot of ideas about the Daemons dex and the various units available--I think I leave off here. Have fun experimenting with all of your new units! And don't worry, you're supposed to be removing dozens of troops minis per enemy shooting phase. A 5++ T3 melee horde army basically guarantees that, unless you go for many expensive MCs and/or Daemon Engines.