so 2 out of 3 screamers are large target (necromancer on mortis engine and terrorgheist) and neither have significant armor, especially the terrorgheist. So a couple of cannons and a wizard (to keep the terroghest grounded) can be very effective. Vampire counts don't have shooting basically, and the scream is only 8". Concentrate on one target (likely the terrorgheist as it can fly) and then move onto the next. A third cannon (maybe from the steam tank) maybe, plus an engineer since you are bringing so much cannons.
Honestly i'd forget trying to demolish the blocks of grave guards as they will bog you down and wear your units do death. A necromancer can easily reanimate 10 each turn, so get the terrorgheist and the necro first ad then destroy the rest with cavalry.
A steam tank is also good if you need to pit down a terrorgheist for the rest of the game, as it will take it a lot of turns to destroy your tank.
The third screamer (the banshee) is ethereal but is also much easier to kill in melee with a character with amgical attacks (or spells).
edit: i read your stillman list. Although i'd have liked one more cannon, basically the same thing but use the wizards to kill the terrogheist and then the necromancer, while dispelling the movement spell on the grave guards as they can be incredibly fast if the spell gets through your mages
