It does feel like the battles are very player dependant until you hit high enough amounts of mobs. Keeping you back line protected is super important. It also does a terrible job of understanding special abilities for mobs or towns. For example there are some mobs with the special ability "immortal" where about 30 sec after they die they will rez, and each time after the chance halves. Using them as a front line with strong ranged is very powerful and can win fights the game says are impossible. Another one is the Pyre faction building, Infernal Gate. It summons units into battle for you based on how much it's upgraded with sulphur. With just a few upgrades it becomes a practically non stop stream of free units that refreshes ever fight. As long as you keep your real units alive it's very difficult to lose a fight after a certain point with enough upgrades.