I found two terrain errors so far (currently exploring the ice cave), one is in the ice lake, where you can move through one of the forest images. Looking at the terrain file, it seems to be those 'possible chest location' terrains?
Also was a bit surprised you could shoot through forests, but I suppose that was intentional
Another bug was in the ice cave, where one corner simply showed a massive rock cube instead. Don't know how to take a screenshot, unfortunately, can't show you.
About balance, well, I suppose characters with light spells have a slight advantage? My thief can't really use bows and other two handed weapons, unless there's another light source nearby.
That's all for now, I'll let you know if I find more.
Oh yeah, perhaps that message box you get when finding wurrick is a bit overkill, for that one sentence