For what it is worth, I think the main problem is the severe restrictions (1:1) forcing you to rely heavily on mechanized covens with Traitor Guard Support formations. Despite being a "kitchen-sink" list, it is the most restrictive Epic list I have ever come across. 1:1 ratio between one core formation and the plethora of support formations plus faction rules. Basically, you need scouts, AA and T-bolts to make it work. The daemon engines (that should be the reason you play the list in the first place) see less use. If you could move what you call Lost and the Damned in that direction, I think it could be worth the effort.

For traitor guards, I think the Vraks list is a good example of a traitor IG with flavour. Straight-up traitors could just as well use the Steel Legion list. The problem is to come up with a traitor theme and stick to it.

/Fredmans

If a list is approved it can be basically left alone. Never to be altered again.
Take for example the Salamanders Space Marine army list. If i want to swap the Imperial Navy aircrafts for say Storm Eagles and Storm Talons i could just create a new list. perhab snoone will play this as it isn't different enough but better this than to de-approve a stable list.

For now I propose to follow this plan
Latd to be updated fixing units and points
Cultist list to be developed -less imperial kit more daemon engines. MikeT has volunteered to put this together

Nearly all the approved lists have been updated

Sounds like a reasonable approach. Maybe add Fredmans suggestion about the 1:1 ratio.