Don't worry. The balance will be there, maybe not perfect right away, but it will be decent. If you look at the monster descriptions before the release of Heroes 5, you'll see that a lot of abilities were removed. There's no need for anti-magic or runic magic; otherwise, everyone will have abilities, and it will be possible to remove it from the Dwarves, which is not good... Besides, the Castle and almost all the units are already made; now they will be testing and fixing...
Regarding the duel, I don't agree with the magic system.