Right, okay I'll try and add my thoughts for you. I'm in agreement with some of Easy E's suggestions, but there is a few I don't agree with, which I shall address in your C&C or later.
Firstly though I must echo sentiments to your overall presentation of these rules. I think you've approached this from the right angle completely, and have obviously taken great care to follow the Gorka model. This may in some cases be overly conservative, but it is the best starting point for tweaking.
I'm not by any means an expert on DE, but I have some experience of them, and used to play them during 3rd ed, but many, many moons have passed since then. I was still a teenager
So, we start at the beginning.
I'd like some more fluff. I know the rules are a priority, but no matter how cheesy it is, I like to see the picture painted. It is quite modest of you to admit the unlikelihood of the Pansee finding Angelis, and of all the races that could possibly end up finding Angelis, it could well be the Dark Pansee, I'd put them (aside of the Tin'eads) as the most likely to, alongside normal Pansee.
I will get to Easy E's comment about the Webway in a bit, but it is safer and more efficient than Warp Travel, and it shares many of the Warps Aspects, including an effect on time. It is not hazard free, but it certainly has its plusses, one of which is that it would only take a Dark Pansee force to get lost in the webway, discover a new portal exit in the webway and happen on angelis by accident. There is also a Pansee craftworld (Alaitoc) suppsed to be in the same segmentum, but at the other side (although this would have a Webway connection). Nearby there is very little, so you are relying on a lot of chance, but it is not impossible. More on the webway later.
Plus, just because GW owns Dark Pansee doesn't mean you can't introduce who they are briefly, even if you specifically refer to the Pansee who turn up.
Onto the warriors. Sybarite, Warriors and Initiates are perfect. I can't think of any necessary changes there off-hand.
I disagree with Easy E on Mechanici, and I think you're right to stick to your convictions on that one. I think a better name could be reached eventually, but Haemonculi are closest to a mixture of Slavers and Doks, and although do have technical knowledge, theirs is limited to implements of inflicting pain and torture. The more complicated mechanisms of the Dark Pansee would be a Mek equivalent. They may answer to the Haemonculi, but these are sadists, obsessed with torture, I doubt they would care much for the weapons of war.
On Haemonculi, I like the idea of Doks, but I think you could take this a bit further, and give it a bit of a unique twist. Dark Pansee are masochistic, even on their own. I would consider adding to the rules some experimentation, on Slaves. My own thoughts are that wounded Slaves are automatically sent to the Haemonculus (any excuse) and rather than fix them, he'll fiddle with them.
In this way, you could end up with Grotesques, maybe even Mandrakes (not sure if Mandrakes are a product of Haemonculi or not). Slaves are my biggest issue, really. What little I know of Dark Elves and Dark Pansee is their feelings of superiority, hatred and masochism of slaves and those they view as inferior (everyone else, who they typically enslave). I could possibly consider some incentives, but I don't think they'd be well equipped, they'd be poorly treated and very weak. I could imagine chucking Slaves into a boarding action on an enemy trukk to prevent boarding actions and then blowing the trukk to smithereens whilst the melee was going on.
You could make them particularly useless in statline, ability, and tendency to make a run for freedom, and justify, if not a hefty price drop, having a random amount free; acquired some way. Slaves are an important commodity to DE, but I'm sure they will sacrifice them willingly, and although they may encourage a killer instinct, it will be combined with physical and mental torture.
As they are, I think they're a perfectly good representation, although I wouldn't allow Slaves to have guns, just basic hand to hand weapons. Grots are slaves, technically, but they thrive on the conditions and are enthusiastic to rewards. In ways they are treat more like servants than beasts of burden. Dark Pansee are a lot less nice, and whereas Grots take a lot to get violent reprisals from, victims of the DEs would take every opportunity to get free.
Nor would I think DE would let them get more opportunities to break out with weapon handouts. Then again, this is just a way of making the DE flavouring a bit more different. The current rules are more than adequate, but there's more you could do to mix it up a bit.
Dark panzee should be able to have slaves...period. No Haemonculi necessary. The slaves work for their masters faithfully in return for better living conditions and less pain. There is plenty of historical precedent for loyal slave troops.
There may be history of this, but I think this runs quite against the Dark Pansee fluff. This entirely depends on how the captor views their slaves, and Dark Pansee are deeply hateful of their slaves, which is why I'd not see them as breeding loyalty, they'd rather just enjoy their agony. I'm possibly with you on having them without a Haemonculi, but I think that horrible arch-enemy of fluff bears in, game balance. For game balance purposes I think you'd need a Haemonculus, and why wouldn't you have one?
Okay, onto weapons and vehicles.
As far as vehicles go, I have one disagreement. The skimmer nature I feel should be represented, and I think the best solution already presents itself in the Deffkopta rules in Digganob on page 89-90. These rules are your best bet, basically you can fly over some stuff, and may crash, but otherwise you'd take buggy, trakk or bike rules for movement. It is a bit more complicated, but it feels right imo. Skimmers in 40k are faster and more mobile but they do pay a higher price for it.
The weapons on glance look good. I'll need to look over the weapons in the DE Codex again before I can be more help. However I would like to offer some suggestions.
Firstly it'd be nice to see some Wych Pit Fighter weapons. This gives the Wyches a unique feature, and as you're going to use them as combat monsters, they should have some unique and cool weaponry to use. The net for instance can be virtually the same to the one used by Runtherds/Slavers in GoMo. The others may take more work, but I'm sure it's possible. It also means Wyches will stand out, and makes Wysiwyg easier.
Secondly, I'd grab some of the Codex update's vehicle upgrades for gubbinz. That'll channel in some of the vehicle modding which is part of the game. You may also want to modify the vehicle permanent damage chart, although this could be a little too complicated, and I don't think it would help much.
These are my immediate thoughts. The rules are more than adequate, these are suggestions for throwing in a bit more DE theme. It depends on how simple you want them. Personally, I highly value simple rules, but sometimes you want it as close as possible.
I also think there should be some special rule to represent the drain of being out of the webway. Perhaps a starvation rule similar to the one in Necromunda for Skavvies? You have to pay a certain number of teef per DE after every game. if you can not, they suffer drain (i.e. Flesh Wounded) until either you can pay the upkeep, or you sacrifice a slave.
That is somewhat possible, I like the idea of the rule, but I don't know of enough of Dark Pansee to know if draining would happen so soon. It seems implied that this is what they grab slaves for, to buy them time. The question is would this cripple DEs or not. With Outlaw/Outlanders in Necromunda, there's usually some special rules that counteract this, so I'd suggest testing out DEs to see how balanced they are before applying additional penalties. The starvation rules has a quite crushing affect on Outlander gangs, and although I can see this making sense in a same vein, Outlander gangs worry a lot about cash, which doesn't feel fluffy for DEs somehow.
Still, I like the idea.