8th Ed. 3v3 battle tactics

I would politely ask your dwarf ally to bring a cannon with the flaming rune to blast the Terrorgheist to bits. Point for point, a horde of great weapon dwarfs will outfight any Brettonian or LM infantry but he can't win by himself. I'd bring a good sized block of Saurus warriors. If the dwarf player feels like he can afford the points, I'd make one his main blocks rangers so you can get the last drop (and make it count).

I would politely ask your Brettonian friend to gear out his general with an assortment of items for fighting characters. As the likely point man he needs to be ready to go toe-to-toe with very nasty vampires and/orc warbosses. If you can swing the points, I'd make sure you have a well equipped Saurus character.

For magic, the dwarf player probably should take a runesmith with the Master Rune of Balance. If you guys have a shared power dice pool, I'd advise you stick with a Brettonian damsel with Light (I think they can take Light) for area buffs. I don't think a Skink Priest will bring much to this party if he doesn't roll a lightning spell. He could caddy a dispel item but dwarfs are better at that.

I'd advise the dwarf player to squeeze as much artillery in as he can afford. This will help you against enemy monsters and artillery. You should supplement your own artillery with LM counter artillery. I'd recommend some combination of Chameleon Skinks, Terradons, and Skink Skirmishers. LM have better light mobile troops than dwarfs or Bretts. They can also flush out Fanatics before said Fanatics will hit the pricey units like Brettonian knights. The Bretts should probably leave the trebuchets at home unless the dwarf player feels like he wants some artillery backup.

The Brettonians should provide all the fast hitting power you need so you probably don't need to take any Steggies or Cold One Riders.

Salamanders are good at burning goblins, most undead, and elves. So I'd bring one at a bare minimum. Remember your Salamanders have the benefit of brave knights to keep the enemy chaff off of them!

For a general strategy, you want to prioritize your dispels against the vampires since undead rely heavily on magical healing (unless the Dark Elves have Purple Sun or some other ueber spell). Try to fight two on to one whenever possible. Taking out characters should be a priority. Orc and Goblins wilt metaphorically when their leaders die. Undead literally wilt when their leaders die.