well dont go so hard on those zombos!
I think they are still pretty cool and bad ass.
why? (non game terms)
GREAT conversion - theme abilities with these guys (still needing to make a thriller dance act by MJackson for a unit, that should be the funkiest dance-dance-death'o'lution unit ever!)
In game terms,
Redirecting! - summon some in front of your enemy facing 45degrees angle. works fine everytime!
speedbump - 20 minimum deployed... well, were all doing some mathhammer.. and taking cav + warbanners and such. BUT! there is the odd chance of MISSING on them/not taking that much casualties! and otherwise, it takes the cav 1 turn longer to plow trough them. You could take hounds/skellies/ghouls. However, they get shot to pieces REAL quick if deployed in low numbers. Nobodys going to shoot at zombies (whoever is right in his mind

)
THAT is in my perspective a GREAT advantage for them. they could move over the battlefield, without being noticed by enemy fire/magic.
Arent those 2 some decent pro's to take em?
horde-play would be very difficult i agree. but ruling them out as complete useless... no way!
I say,

Rob Zombie for president!
*edit, read his own post, and actually its only 1 pro to take em in your list.. the other is just a spell... however, zombies rock, i think every
VC player must have at least 40!

*