About fire vs air, fire is of course more destructive, and may kill the ennemies faster if they just cast offensive air spells (air lack a big ae medium level spell as efficient as falling fires). But most air nation have also access to water 2 mages to cast rain, some may have earth+water for fire ward, and fire indie mages also seem more common than air mages. At high construction levels, any nation having a fire 1 mage can empower him death 1 and forge fire boosters, when a non air nation will need a level 4 mage to start to forge them. Air can finally strike at a very longer range before high levels (once the fire nation has access to spells like pillar of fire this advantage of course disappear
). Finally the kind of national troops Machaka has will suffer against air in mid game (Machaka hasn't medium troops able to survive well against arrows, and the heavy hoplites cost too much ressources if they are to be killed by lightnings, lots of indie infantry with shields will have to be recruited).
At really high levels there are counters to counters, like the use of shock immune summons, earth-fire, death-fire or nature offensive spells, mass protection earth spells etc... But Machaka will have big difficulties if targeted before by an air nation.