When I was experimenting with Destruction Staff (I leveled it to 50) I found that the mouse-click attacks crit based off of spell crit rather than weapon crit.
I do not know if this has changed in the most recent patch.
"If you want others to be happy, practice compassion. If you want to be happy, practice compassion." -- the 14th Dalai Lama Wisdom is doing Now that which benefits you later.