Part 2 of my HQ review. I'll finish up the mundane options here. I haven't dug too deep into the Special Characters yet as in general I'm not a huge SC fan. I'll probably do a post or two on them at the end. Let's start by finishing up the Archon with his "retinue."
The Court of the Archon
The most important thing about this unit is that they are not a true Retinue. As such, the Archon can be singled out in combat, which is probably a good thing for game balance. The Court has 4 options and you have to bring one of each.
Lhamaeans - fail. Warrior statline with +1Ld. Gives the amazing ability to make her and her Archons poison attacks 2+. WTF?? The Lhamaean has 1A and a splinter pistol, so who cares if she has 3+ poison. The Archon brings exactly 2 poison weapons to bear, the already 2+ venom blade and the splinter pistol. Even a 2+ splinter pistol is strictly worse than a blaster or blast pistol, so this ability, as currently written, is literally worthless. We all thought the Lhamaean was the reason to bring the Court at all. If she made all his attacks 2+ poison (2+ poison Huskblade? egads, man) or even 4+, if he could bring a Flesh Gauntlet, if the Agonizer was a real poison weapon, any of those 3 options would make the Lhamaean useful. Right now? Waste of 10 points.
Medusae - Sd6+1, APd6 template for 15 points? I like it. Same statline as above, but actually useful. If you're bringing the Court, I'd bring 2. Templates are one area the DE can find themselves lacking and a double Eyeburst can do some damage as a drive-by or pre-charge.
Sslyth - the "tank" of the group, weighing in at a hefty 35 points. Gets you S/T5, 2W, 3A and a shardcarbine. I don't think he's worth 35 points, but if you bring 3 and kill of your Lhamaean quickly, the Court becomes majority toughness 5 which is pretty silly for DE.
Ur-Ghul - +1S, 3A (but only one CCW) and starts with FC. Supposed to be the CC member of the Court but rather underwhelming at the role for 15 points. I think he needs Rending. Right now, I'd only bring 1 to make it easier to get T5 majority.
Overall, a very underwhelming unit on the table, despite being amazing in fluff and concept. A change to make the Lhamean useful, Rending on the Ur-Ghul (even with an increased cost), some sort of "bodyguard" type rule for the Sslyth to protect your Archon would make the unit playable. Right now, I don't think they have any place in a competitive list. I don't believe GW adequately play-tested this unit.
If you simply MUST include this squad (I'm sure the models will be amazing), go 1 Lhamaean, 1 Ur-Ghul, 2 Medusae and 3 Sslyth for 155. Throw them in a Raider with a Haemonculus and a Liquifier gun. Now you have a very tough unit (T4 on the Haemmy lets you go majority T5 with 1 casualty) that drops 3 scary templates a turn.
Succubus
In direct competition with the Archon for the killy HQ slot (that's right, DE are so badass they get two legitimate CC HQ options). So, how does she compare to the Archon? 5 more points base nets you +1WS and -1BS (not much of a real effect in game), +1I (yay, you get to strike before the numerous I7 enemies out there) and -1Ld. I'd rather have the Archon statline. She also gets a nifty 4++ in CC and starts with combat drugs. Now that's worth 5 points. A lot fewer options though. Weapons are limited to venom, PW, agonizer and whip. Agonizer is the clear winner here. She can take a Wych weapon instead, but since none are PW, the Agonizer is just better. Blast pistol is her only ranged option and it's a no-brainer IMO (unless you NEED those 15 elsewhere). Haywire grenades are the same as for the Archon, worth 5 points, but not a must-include.
So, who to take? The Archon and the Succubus will both be hitting as hard in CC, so that's a wash. If you're like me and love the Blaster option, then the Archon is clearly better at range, but if you're more of a pistol guy, BS7 isn't MUCH better than BS6. The Archon will be more survivable with 5+/2++ than the Succubus at 6+/4++, but that toughness comes with an increased cost. If you're going with a "pricier" Archon like agonizer, djinn/venom or husk, then I think the extra cost is worth it. If you were considering the cheap venom Archon, you'll probably get better play out of the super efficient 85 point agonizer Succubus. I think most armies would loooove to have the 85 or 100 point Succubus as an option, the DE just happen to have a better choice in the Archon.
This article ended up being a little short, so let's discuss a few of the crappier SC that you probably won't see a lot of.
We already discussed the Baron. Vect and the Duke bring enough special rules that they warrant further investigation. Lelith and Malys seem at first glance to actually be worth their points, so they deserve a fuller evaluation. I'm not quite sur about Urien, he can wait. That leaves Drazhar and Kheradruakh.
Drazhar, Master of Blades - 230 points? That's almost as much as Vect. That's a Land Raider. There's no way he's worth that, right? Archon stats with +1S/T is pretty nice. 2+ save is not quite a Shadowfield 2++ but a lot better than an Archon's Kaballite armor. Demiklaives (+2A or +2S) are a lot better starting S4 than S3, so I like that. Eternal Warrior is always a nice ability. Vect doesn't even have that. He makes Incubi Fearless and has both Incubus "exarch" powers so he really excels in a unit of his brethren. However, adding 230 more points the the most expensive unit in your list makes a huge rock that the DE just can't protect. Darting Strike is nice, helping him avoid power weapons since he has no invul. Riposte is a silly add-on special rule (like Seth's dirty fighting) that doesn't really add much. Overall, he's the most beastly CC model the DE can bring. But he's just too expesnive. You can get 2 Shadowfield, Agonizer Archons for Drazhar. "Super" characters just don't work in 5e. The Archon is effective as a choption (choppy option) because he's cheap. Drazhar isn't. Leave him at home.
Kheradruakh, the Decapitator - your obligatory Mandrake SC. He's not a pure killy HQ, bringing some disruption type special rules. He still costs as much as a decked out Archon though (140 points). He brings a S5 PW that causes ID on a wound roll of 6. Decent. No pistol though, so he's always fighting with 4A. Gets Mandrake standard 5++ and Baleblast. T3 and only a 5++? That's not gonna last long. Shade Stalker means he arrives like a Lictor (and also can't charge) so he has a big "shoot me" sign for a turn. Not a great means of disruption. How can GW gets this idea perfect with Wolf Scouts, the mess it up with Lictors and Mandrakes and the Decapitator? Preferred Enemy against one IC is nothing to write home about. Starts with a pain token, which he desperately needs. The verdict? He sucks. If you really need some Mandrake action, bring Mandrakes.
So, Court has character and can be a bad, but not terrible template unit. Succubus make a fine cheap HQ (or in a Wych themed army), but a more expensive Archon is probably better. Drazhar is too expensive for what he does. The Decapitator is just too crappy at what he does (or doesn't do, which is much of anything)