A cavalry WoC list will do quite well against most undead armies. The big strength here is with the exception of the mainstay unit where you will often find the Vampie lord (Blood knights or Grave Gaurd block), undead tend to start with cheap small units in an effort to raise them to fighting strength, saving thier poitns for thier characters and magical items.
This raising of units is going to take 1-2 turns at least, but with your fast moving hard hitting cavalry force you can be charging him and smashing apart his relativly week units before they come to full strength. not forgetting also that mark of slaanesh makes your units immune to fear, terror, and panic (i suggest used on maruader horsemen with flails) and mark of khorne which gives you frenzy means your immune to phsycology, (though i would use the magic banner which gives you frenzy which you never loose).
I would say 3 units of maruader horsemen with flails, then decided wether you want them cheap with mark of Slaanesh or deadly but prone to being lead away with mark of khorne.
1-2 units of knights, never been sure if buying lances has been worth it when you have magical S5 attacks already, but give one of these units banner of Rage and maybe mark of nurgle to go realy expensive but worth it.
I think the big thing to consider is characters. do you go for the sorcerer lord and two sorcerers on discs of tzeentch or go with a suttle magic deffense and hard mounted heroes and lords? after this you may have between 1300-1000pts roughly depending on how you spend etc.
But to answer your main question, as long as you dont sit back with your WoC against his VC, and you dont reklessly charge into obvious zombie tar pits or his lords units unsupported you shoudl do better than ok.
