Wil is known for having very bad dice rolls, most often rolling natural ones and single digit numbers. He refers to this as the "Wheaton Dice Curse". Of the 54 rolls he performed during his guest appearance, 10 were natural ones. A "fair" dice should have rolled an average of 2.7 natural ones in that scenario.
CritRoleStats did an analysis of Wil's dice rolls over the course of the two episodes in which he appeared.