Obviously you can't use Drazhar in a Wych Cult (no Incubi) and similarly Urien can't really be involved either.
Thanks for beatin me to the punch Alex! I must be slow this morning!
If you read your codex silverburner, you'll see that Drazhar replaces an incubi in the Archon's retinue. He's your run of the mill, champion badass incubi. Mernil was absolutely correct in stating that more than 5 or 6 incubi are just plain overkill. While I LOVE the model, and Drazhar makes a retinue just plain nasty, he also puts it into the overkill departmant, and so unless I'm just playing for fun, I usually leave him at home.
The reason you DON'T want your HQ to be that uber, is that there isn't much that squad can't slice right through in a single turn. While this doesn't sound like a bad idea, that also means that your uber HQ is now completely vulnerable to shooting attacks on your opponent's turn. Taking 5 or 6 incubi, while still a formidable squad, will usually leave one or two left standing that you can finish off on your opponent's assault phase, thereby keeping them safe from shooting attacks. Making very large uber HQ squads is a common mistake of players new to DE. Keep in mind, that sinking that many points into a single unit, also makes a nice juicy target for your opponent to pour every last shot he has into.
That is all.
CrimsonShadow