HQ's. The Archons base wargear is a joke compared to an Autarch. His better stats don't really make up for this. He should at least have the same armour as scourges who can afford the best armour in Comorragh (outside of the Incubi "aspect" armour). Stock this makes the Archon a reasonable HQ choice. He should have access to bikes, boards and wings so you can kit him out to accompany other units if you like.
The Succubus should be more scary in combat to account for that horrible S6 insta-kill weakness she has. I dunno about her getting access to bikes and boards though, she seems like a pure Wych style fighter to me.
Haemonculus' are over priced I think. They don't have amazing stats and don't really have cool rules like a lot of other HQ's do. I think its best they're cheaper and to have more of them. Boosting several units with +1 PfP seems a good use of them to me.
Lets talk troop changes reasoning. The biggest change really is that troops in transports should not be hamstrung by the speed/manoeuvre restrictions of the lesser races. Units should be able to assault form vehicles moving at cruising speed and they should not be hindered from firing from them. Our transports should always be moving 12" and that should not cripple the effectiveness of the units they're carrying. This will re-crown the DE as the kings of speed and repositioning in 40k.
Trueborn need a boost because they're just too expensive for what they do. They're meant to be the aristocracy of Comorragh, the foot knights fighting their way to the top. They should have better stock arms and armour. Their upgrades need to be cheaper also because when you mathhammer them out they're not really efficient. Giving them BS 5 though seems OP and unfitting.
Bloodbrides need a significant boost. They should be on the same level as Incubi for fighting. they just have a different role. Their role is to engage large infantry squads (Ork Boys for example) and rip them to shreds. Not be an elite choice tarpit. I've not inclued any changes to Wych weapons but I think they're needed. 2/3 of them are crap and one just gives shred. That's crap. I'm hoping somebody else can suggest rues to change them (that aren't OP). With changed up weapons and these changes then taking elite Bloodbrides (and using Wyches at all) becomes appealing.
Incubi need something to offset their lack of overwatch. It's dumb they get nothing at all in defence when they're meant to be employed as bodyguards. Counter-attack is perfect. Doesn't matter if they charge or are charged, they're getting those extra attacks. I purposefully didn't give them plasma grenades (whilst I did practically everyone else). Although they can be used as shock troops I don't feel this is their role in the list. Buffed Bloodbrides could do that much better (assaulting from a Raider moving at cruising speed). I want these guys to be counter-attacking (in a strategic sense), to be thrown in to turn the tide of battle as the Triarii of the army. I didn't want them just being heavy assault troops.
Hellions needed the biggest change. Moving them to troops gives you the option for using them in place of Kabalites or Wyches as your go to troop choice. you can have an all jump army if you like. They needed the obvious grenades and I feel their skyboards should be just as good as Reavers in dishing out HoW attacks. I don't thin they should get +1 A as many suggest, they're not elite combat troops like Incubi or Bloodbrides (who do get the +1 A) and they're using two-handed weapons. That comes at a cost. They do however hit at S4 which is an advantage other DE lack except for Incubi. They could even hit S5 with combat drugs. If you want to devastate an enemy unit then you should take more of them (upto 20). Otherwise they have hit and run to extricate themselves from tricky combat. A novel change I made was giving them Battle Focus (or a DE version of it). I felt they should be constantly moving towards the enemy. They don't fire their guns themselves, they're mounted on the board itself. Makes sense they'd be charging headlong at the foe just shooting in front of them. This bonus would also help them keep pace with an army that can assault from cruising speed transports.
Solarites in Scourge squads should get a DE version of Herald of Victory. It would justify the points cost of taking a Sybarite in a squad where otherwise you just don't need a character. Would make choosing heat lances more appealing and add tactical depth to the choice of weapons to equip them with instead of asking "will I DS them or not?" and using that as to answer the question.
I didn't feel that the other infantry choices needed changes. Grots are good already with their formation. Wracks are ok but they're meant to be the standard troop choice of a Coven army so I didn't want to make them stronger than that role would require.
Vehicles needed some adjustment. Every vehicle should have the option of flickerfields or night shields. NS are better and cost more but are vulnerable to ignore cover. Flickerfields are safer but weaker. Though you might have tactical reasons for either one of them that ignore their relative strengths. I like how they work but they should both be options.
All transports can move at cruising speed and still allow passengers to disembark and assault. All vehicles allow passengers to fire as if stationary (this is up for debate whether it should just be relentless for heavy weapons or stationary for rapid fire too). The point being that transports should not be lumbering around at Leman Russ speeds just because they have passengers. They should be blitzing into the enemy lines without crippling their passengers by doing so. We're supposed to be fast and hard hitting right? Transport capacities also increased in line with what Space Marines have. We should be ale to put IC's into transports with our squads the same as speshul marines (who used to have the same problem too until they got buffed). Ravagers get Aerial Assault back because WTF? Why have the DE made a 3 gun platform that can't fire it's 3 guns effectively. Again this BS of slowing down the entire army just do anything. Ravagers should be cruising at 12" with everything else and not be handicapped for that. Again, speed. I don't feel that Ravagers warranted having void lances as an option. They don't need them. They're role isn't super heavy tank hunting, it's medium battle tank hunting. And they're pretty good at doing that now, especially in numbers. Keep them cheap, have more of them and let them shoot multiple anti-tank weaponry.
Razorwings/Voidravens should have Vector Dancer. Simple as. Can this work with Supersonic? I dunno if it does but it should. They should be super fast and super agile at the same time. They should be able to take the same flickerfields and night shields as everything else, you take these to taste. Voidravens get some targeting buffs to cement their role as super heavy hunters. Their bomb hold be D, this makes sense with the escalation of units on the table and its role as a bomber. I think the lances are fine as is though. They're superior to dark lances for some extra push but aren't OP. A little reduction in missile costs makes them a bit more competitive. They'd be pretty good counters to a lot of the big crap on peoples tables. And you might consider taking two of them.
The forge world vehicles needed some adjustments. Reaper lost a bit of S on it's gun, didn't make sense considering it's a beefed up haywire gun. It had insta-death rules anyway which made the extra S redundant. The Tantalus needs a cost reduction but I'm not sure by how much. The finer points of points values are not something I'm familiar with. The scythevane rules need changing because no longer do models fly over others and damage them. Best I could think of was making them work like Ork Deff Rollers. They should be better at tank shocking though because those blades are SHARP and the DE are just scary!
In terms of weaponry shard carbines should be more plentiful and not limited to a single unit only. Splinter weaponry should get the same rule that shuriken weaponry gets - they're supposed to be the same tech except the DE add poison to their ammo (and use a differently shaped fragment but that's just getting technical). They should be hitting at AP2 on 6's. This might initially seem like a massive buff but if you look at Eldar units they're specialists are significantly stronger in their roles than DE specialists. I think DE base troops should be better that their Craftworld cousins.
Dodge. Why this doesn't apply to the charge is beyond me. It's a dumb oversight that makes using Wyches dangerous in the majority of circumstances. This simple change means Wyches can charge in safety. Maybe they'll even charge Tau? The better Wych characters - the Succubus and the syrens should have an improved version of dodge. They should be damned hard to kill in melee because they're so easy to kill outside of it.
One change I'm considering but aren't sure of yet is dealing with ATSKNF. It annoys me that a lot of the DE tricks don't work on marines but this doesn't make sense. They're not fearless. And they're scarred of a bunch of things (including chaos influence/subversion). You'd think the master mind-feckers of the galaxy would have the tech necessary to overcome speshul marine genetic resilience? There's no way the speshul marine battle trances and mind control techniques are better than those coming out the Craftworlds and our torment devices work on them. So why not marines? I think the torment/phantasm grenades and the wargear that cause wounds etc on failed leadership checks should work on marines. Unless they're fearless. But there's still debate over this issue.
Sorry for the length of posts but this isn't a subject you can cover in a couple lines! Lets discuss this and see if we can reach a consensus on what is needed to make the DE work as they should.