The Scalings on Pick a Card's damage should be different, not the base damage.

As it stands, each card in Twisted Fate's Pick a Card has a 1.0 AD scaling (since it's a basic attack) and a 0.5 AP scaling. The base damages are why blue hurts more than red, and red hurts more than yellow.

Red cards have 75% the base damage of blue cards, and yellow cards have 50% the base damage of red cards.

The problem is that as a mage, Twisted Fate has a very small window of time where the base damage of his spells is a significant portion of its damage. At rank 5, a blue card has 120 base damage. By itself, not that powerful. With Lich Bane and Luden's Echo, it'll do a good chunk of the enemy's health bar. Except he could just use a yellow card and get the same burst (-75 hit points of damage) while stunning you. As it stands, he has no reason to use blue card when fighting.

If instead, each card had a different scaling, there would be more of a strategic element to this spell. If there's a cluster of enemies, it's still better at the moment to stun one of them and assassinate them. If yellow card had weaker scaling and couldn't burst most people when paired with a cast of Wild Cards, TF would have more incentive to pull a red card, dealing decent damage to the group while slowing them down. (Of course, there are still cases where getting the stun would be better, such as if he can reach a high-priority target).

The biggest problem in implementing this change is trying to find the right numbers (or compensating other things when we can't). TF isn't in a position to get a flat nerf, so we can't just reduce the scaling on red and yellow cards. But if we give that much more damage to blue cards he'll be able to assassinate people even without the Q. And it would be difficult to compensate yellow card with anything, as it's already a 2 second stun on a 4 second cooldown.