In my mind, having a lower normal is a plus, for making the recipe items for Carpenter, Smith & Bowcraft.
Consider, a 30% Exceptional bonus.
IF you have a base 70% to make an item, and 10% chance of it being exceptional -
A 30/30 talisman will have you succeed 100% of the time, but only 40% will be exceptional.
A 0/30 talisman will have you only succeeding 70% of the time, but 40% of that 70% will be exceptional.
In the first case, 60% of your successes will be normal.
In the latter case, (3/7 * 100%) = only 42.857% of your successes would be normal. You'll more of the wood you're crafting from, but the gems aren't consumed on a failure, the way they are with tinker jewelry.
That's why I keep a high-both AND high Exceptional-Only talisman for crafting skills.