I think that Preordain is instrumental in combatting Workshop decks especially for tempo strategies. I do think that Mentor needs to be restricted because it is probably more efficient than Yawg Will and Tendrils combined. Not only is it just as powerful as both cards, it can be played on one turn, and then it can be used on the next turn with more mana further increasing its effectiveness. Restricting Mentor would not end the token strategy because Young Pyromancer can be used in combination with Mentor. I also think Gitaxian Probe should be restricted because it undermines a fundamental element of the game that enables various strategies to be implemented by: the ability to view the opponent's hand, draw a card, pay 0 mana, and then obtain the information to potentially carry out one's own strategy without flaw. This too much to be done more than one time without the help of another card such as Snapcaster Mage or Jace, Vryn's Prodigy. The combination of Mentor and Gitaxian Probe go against any strategic rationalization that a format should stand for. Playing a 56 card deck with the most efficient win condition in the game is further taken advantage of by Mentor's ability to gain from anything except creature spells and land. This requires no planning once the card is in play.
Paradoxical Outcome is a card that when it is nearly at its worst amounts to an Ancestral Recall with additional mana open. Although I cannot justify calling for its restriction I think it is more worthy of being restricted than Dig Through Time.