Re: Why no heavy cavalry?
well in the low fantasy game, our country hadn't invented stirrups, so mounted combat was unfeasalbe. Then once we had stolen the technology, we had the cost problem, because training warhorses and knights costed lots in money and time. So we had at most 20, for one battle (like we only used them once).
In a high magic environment, it's just as effective to put a shield on the horses, so that the fireball breaks before them (a forcewall).
Remember that as offense increases, so would defense. An example of this is in the "Sword of Truth" series (i belive "faith of the fallen")