Ancient steg wouldn't be so bad, all three are very susceptible to poison. 4D6 +3 poison shots will often be better than charging him in, especially against Rat Ogres or Minotaurs.
I haven't fought the noew OK book yet, so I'll leave that to someone else. I can give you tips for fighting Beastmen and Skaven though.
Your priority target for both will be taking out their BSB. BM can use it to reroll primal fury, this is a Very Bad Thing. Skaven depend on the reroll to stick around, especially if you can flank them to take away Strength in Numbers (where they add their rank bonus to their leadership.) Consider a Skrox unit (22+2 with Std/Mus) that can be used as a headhunting squad. Do not challenge Skaven as they can retreat to the back with no ill effect.
Salamanders are definitely your friend for softening up the hordes you will see.
Do not skimp on magic protection, depending on the points you play at try to add both becalming and a scroll caddy. Save your scroll for the dreaded 13th.
Make sure you have something with flaming attacks that can kill off a Hell Pit Abomination.
Go with either Lore of Light (for boosting your Saurus blocks) or Lore of Life (Dwellers to thin out hordes).