hordes are 10 wide and therefore gain that 3rd rank's attacks - 4th with spears. With spears, full command & the banner that allows you to count an additional rank you're looking at investing 405 points
While I haven't had much success running 20-blocks of skeletons I really can't see the call for hordes of skeletons. They're sub-par fighters unless successfully buffed with magic, or the crown of command. My thoughts are that without a successful buff (or failed fear check) skeletons are such sub-par fighters that you should really still be trying to maximize your static combat res while at the same time minimizing the number of attacks your opponents can throw at you. By increasing your frontage up to horde-size you're increasing the number of attacks that can be thrown at you by wide units as well. By running that same 40-block of skeletons in a 5-wide x 8-deep block you're almost always going to be denying your opponent's steadfast while forcing any of his horde units to miss out on several files worth of attacks (20mm bases will miss 3-files worth of attacks).
Obviously this unit would provide a pretty tasty flank - but I think that's where vampires shine. We're able to create our own flank protection in the form of zombies. While we can't use these guys to direct charges away from us as effectively anymore we can still delay them a turn or two.
Ghouls on the otherhand have the offensive and defensive potential to consider running wider. With an additional point in almost every stat AND poison ghouls are considerably tougher customers. Obviously still the more competitive choice. But since you can't give them spears they only really need to be 3-ranks deep (setting you back 248points).
Either way you go I'd recommend running the minimum number of ranks to be effective - if you run a skeleton horde with spears run 4-deep, HW/S hordes only need to be 3-deep; a ghoul horde runs 3-deep. Vampires should be able to keep their units at full fighting strength if not increase the sizes.
