The Hordes of Undeath aren't like any other race in the Warhammer world.
Most troops cause fear and are immue to psychology.
The Undead army can be divided into three types of units, the missile fodder, barrels of wounds, and the Lords of Undeath. The basic Undead troops, Skeleton Warriors are way too expensive. Their high cost and sub-average stats makes you want to cry and laugh at the same time. Although they don't break and cause fear, they aren't justification enough. Zombies led by a character with Crown of Command are much better deals.