Taco I just beat mountain fire, I put all of my guys in the middle region, and started building from the bottom. I put warriors on corners and mages between them. From the beginning I upgraded all mages to cold, but put most of the warriors to physical. After the two waves that resist cold I started upgrading everything to cold. On each indent I upgraded one mage to slow and one to debuff. On the islands I put infect mages. The infect mages I upgraded damage, the destructor, and the other mages I upgraded one level of specialist than destructor. Warriors I gave critical to and did not upgrade past that point. I also used a cold mage hero.
The Pancor jackhammer is a real weapon, it is not very practical, and is not really used by anyone, but it does put out a ludicrous amount of firepower. At close range it's basically a disintegrator beam.
This game is a good idea, but kind of sucks. It is really stupid that the units only do 1 damage to defending enemies... I can't imagine why that seemed like a good gameplay element. I didn't have the patience to try to get deeper into this game.