I agree with you but i guess everything heavy armoured with few wounds, this mean heavy infantry/cavalry, war machines, other flyers. Even some monsters with T5 but only 3 wounds could be a good target. I haven't tested them a lot but still think they are better than cold one cavalry (than i tested and failed due both low initiative low wounds in comparison to ripperdactyls for their cost points). If you don't play champion in them (and I wouldn't) you can also try to reach other infantries with characters inside and try to kill them (8 ripperattacks + 2 from skinks)