Playing agains ogres you have to concentrade to take out the butchers because they crap without them. Giants are not so good as they like because...
I think about 5 in a unit, the cold one cavalry is a very hard hitting unit but they are really expensive. But with this unit in an enemy flank...
3 terradons are enough to take out warmachines and light units, i mostly play with 3 or 5 terradons.