Let's not forget this is an alliance battle and the lizzies don't have to do all the heavy lifting. Here are a few ideas for what each army can contribute:
Vamp Strengths:
1) the DP - A couple terrorgheists could take out the DP. With the FAQ the shriek can now be cast into combat so simply keep the terrorgheists within 12" of the vamp general and they will be able to fly in and smoke the DP whether or not it is in combat. Also, they could take out hellcannons, RBTs, chariots, monstrous cav, etc. This might even result in the DP avoiding combat and trying to run away from the terrorgheists (which is just as good since he is not in combat earning his points!!)
2) tooled up vamp lord - tooled up mounted vamp lord with ASF, red fury, ogre/giant/obsidian blade & other stuff could chew through anything in a WoC or HE list and can even give the DP a run for his money.
3) chaff - a host of cheap units that can be used to tie up, deflect or delay the enemy. Dire wolves are particularly good since they move 18", are way less than skinks and can vanguard.
4) Vargheists - the perfect unit for taking out the high elf rear area troops. With skirmish, fly, stomp & loads of S5 attacks, S3/T3 elves will get crushed. They would also be excellent flankers against more elite infantry units.
5) Hexwraiths - risky but very good if used carefully since the drive-by S5, no armour save attacks can take a few wounds off of skullcrushers or even a DP.
6) tar pit - zombies & ghouls do very well in this regard. If supported by a corpse cart, the units can be even more effective.
Now, there are a few areas where the vamps are relatively weak that lizzies can really fill in the missing pieces:
1) scouts - 2-3 decent size units of chameleons to go after war machines or squishy elf infantry/archers. Deployment may be challenging due to the enemy deployment area being filled but careful selection & place of terrain should help this by creating hiding spots behind buildings/monuments, etc.
2) template shooting - Sallies are devastating against elves and a couple decent templates on a horde of WoC can ruin their day, kill far more warriors than is possible in a round of combat and it causes a panic check to boot!
3) mass shooting - skirmish skinks are great for taking on expensive elf troops and cheap enough to be disposable.
4) roadblock heroes - scar vet cowboys within 12" of a LD 10 slaan can be expected to hold up a WoC death star long enough for a flanking unit to move into position and then charge in to get the necessary static res working in your favour. Vamp heroes can't do this as they crumble when they lose.
5) units that don't die in droves - saurus & TG will lose against WoC but the will not die in the masses that vamp infantry will. Toss in a life buff or two and the units become amazing. After that, flank them with black knights (& the chopomatic vamp lord)/saurus/TG and let static res do the rest.
6) Magic - Slaan rocks the magic phase and is great on defence as well. Vamp magic is far more subtle (i.e. ineffective). If reliance on vamp magic is minimized, the vamp general doesn't risk miscasts and can be better tooled for combat.
All this to say that each army can bring some excellent capabilities to the field to complement the other. Key is to coordinate the overall army design with a plan in mind on how to get the most out of them when its game time.
