I've had a few games with a big block of these. I find that whilst they tar pit nicely their damage output means that once engaged they do not participate much more in the game.
I have started to look for an efficient build which can take out two larger units in 8 turns. The below unit I think benefits greatly from a support unit of bowmen or two and having Ankaur Maro floating around will keep them even more effective. I stayed away from the x12 unit as i think there is diminishing returns here and you'll lose army wide capability.
Reanimates x9 - 87 pts
--Champion: Ardus IxErebus - mainly for the white dice, but can add blight from nearby archers
--Heavy: Front Line Carrion Lancer - tunrs blight into mortal wounds
--Heraldry: Blighted Vexillum Bearer - 3 pts for a free blight
--Music: Triumphant Cry - here's the item to get this unit into a second combat, the free reform critically saves a turn which is often required to get Reanimates point in the right direction.
--Training: Lingering Dead - keeps the unit going, so often I have lost exactly 4 models it is frustrating.