as previously said, drop the webway and give the archon a phantasm to go with the incubi.
I would suggest swapping the night shields for enhanced aethersails on your assault based raiders you want them in the enemies face before you get shot down, as this gives you an extra
2d6 movement and you will be getting a cover save from moving anyway. have night shields on your shooty vehicles.
also I would mount the warriors with the splinter cannon in the raider instead of the ones with the lance, as you need to keep moving therefore your warrior will be firing his lance at BS1. splinter cannon is assault 4 heavy 6 so you have the option to snap shot 6 or fire 4 at full
BS. if you can, get splinter wracks for that raider too.
personally I would drop the first archon and have a succubus go with the wyches instead,
succubus
venom blade
haywire grenades
75 pts
she fits in much better I think.
just my thoughts.
a few things I have learnt since playing dark elder have been:
Pain tokens, combat drugs, dark lances and movement are your best friends!
Try and get pain tokens wherever possible, whether from preying on units that have been whittled down, from combat drugs or from units that have altered physique (coven units)
try and get combat drugs on your characters wherever possible!
I hope I haven't waffled on too long