They were not useless infact they had a heavy hand in dealing with the thunder king. Also they seemed so out gunned do to the fact they had learned to suppress their negative emotions to a point thus the Sha had never manifested this bad since the last emperor. Then in comes the horde and alliance with their as he put it race war and the Sha FEAST and appear like never before. They are the best equipped to deal with the remaining old god/sha corruption and most logical option. The alliance will want hellscream and the horde will say no we want him. Don't give me the alliance could just take him as the moment they leave Org that chance is lost.