1. I go with 1 single unit of Crypt horrors. I do not like the cost of vargs. My army is also all on foot and the vargs outrun things and get too far away from other support units.
2. I do not bother with the mortis engine. I would rather just start with larger units.
3. I have never used a ghoul king.
4. Sometimes in my killer grave guard/vamp lord unit I have a wight king with the obsidian lodestone. This gives the unit and my general a ward save against magic. My vampire lord is geared to be all attack with no ward saves. The wight king also benefits from the banner of the burrows.