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Well, I actually really love Water magic :) And instead of spells like Chain Lightning or Explosion, I prefer Mass Prayer, Healing, own Divine Blessing and Forgetfulness (though it also depends on the circumstances—the smaller the army, the more powerful combat magic becomes)
But Earth has the same "cheater" spell as Town Portal, and Air has incredibly cool Astral Gates; and Haste and Slow, the two most powerful spells in the game (given roughly equal armies and the presence of shooters), belong to Air and Earth.
For a while, I also took all 4 schools of magic, but then I concluded that there are other skills that are just as useful (for example, Logistics, which I think is even cooler than all these magics!). Besides, I prefer playing on small maps and at the highest difficulty level (I mostly play against the AI :(), and as you can imagine, that brings some changes...