Commorragh is an eternal dark city, hosting millions of crusades for lots of stupid reasons (just ask Vect). Logically, Dark Eldar should be here then!
Imperial Guard. I don't see the Problem on Balancing them eather. Ork Boyz aren't that much more Effective, Eldar Guardians neither. Tau Firewarrior is basicly just an Kasrkin with much less Experience and Training. Also most Battles of the Guard aren't 10 Million Soldiers Against 100.000 X while loosing 7 Million in the process. That would be an Battle remembered for Centuries. At Most Battles we have 2-20 Regiments of the Guard fighting alone or with the Planetary Defense Against Tyranids, Chaos Traitors or an Orc Whaagh while still having fair Chances of winning. It's also very important which Regiment is Fighting, Cadians have MUCH less losses than other Regiments, there were even a Battle were the Cadians defeated an entire Swarm Tentacle while not loosing one entire Unit of Soldiers. (gotta admit, the Unit survives if only 1 Man survives.) So please get rid of this IG Myths. Many Guardmen can really pack a searious Punch. The only Balancing Issue in Eternal Crusade is that Tactical Marines are presented as puny Regulars while they should be the Advanced state, Scout should be Regular.
I'm somewhat thinking Traitor Guardsmen could be Stronger than regular ones considering how much the Chaos Gods grant you something. Sure not stuff a Chaos Marine would get but why shouldn't Khorne be pleased if an weak Human kills 4 Guys as Strong as him all at once?
The reason for the "purge" was not because of people sow some Grey Knights, it was because the Inquisition didn't want the taint of Chaos to spread. And the only reason the planet wasn't just destroyed was it was deemed to valuable of a resource to get rid of. In the eyes of the Inquisition the need to contain chaos justified the "purge", the Grey knights actually were apposed to it but followed orders. The Imperial Guard wouldn't even know who the Grey Knights were other than the fact that they were Space Marines. The battle of Armageddon is a good story, but it doesn't give any reason for the Grey knights to not be in EC. It more points out why one Inquisitor Lord should not have that complete control over that many forces. Do not blame the actions of the Inquisition on the Grey Knights.
I used to have 2 table top armies based around traitor/possessed guardsmen, a Chaos cultist army (with a mix of guradsmen, necromonda troops and daemons) and a Genestealer cult ( a normal IG army without command units, several mutations such as extra arms, stealer swarms to back them up and a Genestealer Patriarch).
