Aspyr's official Gothic 3 website has been updated with an in-house Q&A in which executive producer Blaine Christine answers questions about the upcoming North American version.
How does playing as a more pure magic user change how you play the game, or which quest routes you take?
A pure magic user is going to play the game very differently from a more balanced character build. If all of your Learning Points are going into Ancient Knowledge, then that means you are going light on Strength. As such, a pure magic user will be spending a lot of effort and mana to keep enemies outside of striking range or even avoiding combat altogether with some magic trickery (which can be quite entertaining!)
If your character is completely invested in magic, then you will most certainly be avoiding the arena combat quests since magic isn't allowed. However, you will find that those big area effect spells that you've worked so hard to obtain do a great job of taking out those strong enemies that you'd otherwise have to spend ages trading blows with.