Manfred goes in big zombie bunker to start and leaves if it gets in combat
Manfred can't leave the unit if it gets engaged in
CC, even if manfred himself is not
B2B with an enemy model.
For 2250 I'd drop manfred for a master necro, and some wraiths/wight kings. Place the wraiths/wight kings in your skelle blocks to add more hitting power to your core, or to your grave guard to turn it into a beast to deal with in
CC.
Your vamps are way under protected. I'd drop some of the powers to pick up at least solid
AS for them, but a ward save would be better. As is; T4/2W/4+
AS is not that hard to push through, even with chaff troops.
You could even drop the vamps all together and run necros in their place. You'll have the same casting power, but not have to worry about having your casters also having to carry your skelles in
CC too. If you do drop the vamps, it just frees up more points for wraiths/wight kings to be the
CC punch in your blocks.
Terrorgiests are good, but I'd swap one for some crypt horrors/vargiests.
Horrors are a rock, and very hard to shift if you can keep casting invo in range of the unit. Vargiests are very fast, and hit very hard. Frenzy is not that hard to work around, and the unit can do some real damage if it gets in the flanks of an enemy.