"On 2+ the miscast is ignored an if there is enemy wizard withn the line of sight he will suffer its effects, ignoring results 5-6." Its slanns...
Yes, you can choose in wich order to use items. But still ToVs description says "Every time the wizard miscasts, roll a dice. On a 2+ the miscast...
But the Throne of Vines spell says "Every time the wizard miscasts, roll a dice. On a 2+ the miscast is ignored." So every time slann miscasts...