Really, Crusaders would do really well in this. I'd probably go for 2 crusaders, one skill class, and one dragonfire adept. The adept does control/mass damage, the crusaders focus on healing and defending, and the skill dude does skills.

One thing, have some choke points, and make sure that while the first couple rounds it always works in the Players favor, but as the undead get smarter/tougher, have them use it as well.