Oh boy I remember that one. I had to restart several times before I got it right, but I don't exactly remember what I did. I think I made a dwarf army with lots of healers. I think I also had rouges as well. The dwarves do wonders in taking out those buildings, and I had a 4 man pwnage squad of rouges (one was like, a lvl 23 lord). Dwarves stun and rouges stun -- it's very useful to take out those heroes before they run away. Your hero setup can really make the difference between victory and defeat in these missions. I had most of my heroes defending key positions of my base, mostly the north and east because thats where the enemy attacks from. I would only set attack bounties on one area at a time and made the bounties large enough so that one group responds.
Do not reveal/destroy the range hut early! Wait as long as possible until the revolution starts. Good luck! You will need it as there are far greater challenges ahead.