I finally got word back from Mephisto about the characters!
The problems with the Magician Apprentice are an interesting take on the
character's ability. Indeed it is not intended that the character casts
the same spell over and over again. To remove a spell directly from the
game would be also problematic as this ability could be used
aggressively to get rid of certain spells forever. Therefore there are
1. When the Magician Apprentice casts a spell, instead of putting it on
the discard pile it is put below the other cards.
2. The character has to alternate between between drawing from the
discard pile or the spell deck.
The second solution contradicts the card, so I would favor solution 1.
The idea of the ability was just to give this character somewhat more
freedom in learning spells.
Regarding the Black Witch: This was just an error, the starting location
should be the Deep Forest.
I'm going to go with solution one, it's more in the intended spirit of the character.
Apprentice Mage's "fix" for information.
Perhaps rather than place it at the bottom of the Spell Pile, you could shuffle them into the Spell Pile instead. But then again, that is a change to the intended character...