The only suggestion I have is place the shaman in with a unit. He is pretty tough and can stay on the ends of your hordes. You might need him closer to the action for his spells. Such as savage beasts of horros.
I'd consider a larger bunker for your shaman if you go the bunker route. All it takes is a single casualty to the ungors and then he no longer gets a Look out Sir! against templates, and shooting attacks will start hitting him if there's enough of them.
Also don't neglect jamesacon's comment - if you go lore of beasts a timely transformation into a hydra can win you the game!
Have you thought about either dropping the level 4 to a level 2? That great bray shaman is very naked and those raiders aren't going to do much
Alternatively have you thought of dropping the Beastlord and just running a kitted out Great Bray? Level 4 ward, crown of command and maybe the +1 strength sword (I think the beastmen book +1 strength or +1 attack sword is cheaper than the big red book version).