The quest “Soften them up” can’t be completed anymore since the mythic version launched. No matter on which version you enter, the 0/15 Twilight’s Hammer Minion slain stays the same. You can still get 30/30 trogg dwellers slain, but not the hammer minions. I’ve posted a bug report since its mythic release (so a few months back), and it still hasn’t been fixed.