Holk

This is probably something that would be worried about after more than the first area in the game is working.

As far as creature spawning goes, a last resort could possibly be making custom creatures for the areas that are difficult to balance. This would be pretty time consuming, however. With the stat variables and item drops, this option would be far from ideal. With the mage A/I, I don't really know what you could do besides tweaking the scripting to make it resemble the 3rd ed. rules, but I'm sure you already know that.