Nice army!!
I personally have found that shamans definatly pay off with the O&G, lots of power dice ^_^ I agree with everyone else, take out the doom diver, and increase unit size. One thing of my own, maybe put in some wolf riders, lots of speed
They can be very helpful if you can keep them from dying in the first few turns. Squigs and fanatics are always great fun to have, thats all (Y)