I agree of course that spell times should be increased depending on the difficulty of the spell. While pure magic users should be frail, let's not forget that they can study protection spells to counter balance their lack of being able to wear any kind of heavy armor. This particular breed of mage should have the largest variety of spells, but would require players to experiement with components to create recipes. This would offer a really diverse dynamic to the game, making everyone's experience very different and unique.