Ill sometimes run a few units of only 20 zombies and after a turn or two of IoN-ing them, they can be almost 40 strong or more. Chariots and monsters are more than welcome to try to kill off a unit like that. In the mean time, I can either scream away those tied up units, or deal with the unsupported bulk of my opponents army. Our army can make great synergy between units. If I chaff up (and I mean like deep zombie rank chaff) some enemy flanking units, I can use a hero supported block to take down the enemies main force, and what better way to wittle down the enemy's best unit than use a TG in tandem with my killing block?
Not into TGs? I think the ME turns our army into the most ridiculously stubborn army for opponents to wipe out. Double ME doubles that toughness, making zombie chaff units frustratingly good at what they do. Plus the option for additional casting power is also great. This also turns ghouls into very resilient and strong blocks to be led by a hero.
Not into ANY of our rares? You can use CHs, BKs or GG as hardy blocks to tangle with enemy core and specials. Use vargs to clean up back fields and sniff out wizards.
Those are all examples of things I use to really give the punch with VCs. But honestly our core works well, zombies can be bought or simply raised and then extended to hold down units that are going to team up against yours. Wolves can be used as speed bumps or sometimes I use them to hunt warmachines and the like; similar to vargheists except weaker, cheaper and core...er. Skeletons are my bread and butter for putting heroes in. Ghouls are a better choice than skeletons for killing power, but I also sometimes use small, independent units of 10-20 ghouls as skirmisher destroyers. Non-combat units don't stand a chance against ghouls.
Our core is good, you just can't throw it against most things standalone and expect them to win. If my core goes in unsupported, then the target is either weak, vulnerable (to ghouls mostly), or is a unit that I expect to be teaming up with other units against mine.