Another feat for casters

This is a work in progress!

Implement Proficiency
Benefit: You gain additional use out of a single implement of your choice.
Special: You can take this feat more than once. Each time you select this feat, choose another weapon.

Orb: Allows you to ignore the first 5 resistance against any power that you channel through the orb.
Wand: Any power used through a wand gains a +1 to hit.
Staff: You gain +1 AC and +1 damage (per tier) with any power channeled through the staff.
Rod: Any rod wielded by you gain the high crit property.
Totem: ?

High Crit: A high crit implement deals more damage when you score a critical hit with it. A critical hit deals maximum weapon damage and an extra 1d10 at 1st–10th levels, an extra 2d10 at 11th–20th levels, and an extra 3d10 at 21st–30th levels. This extra damage is in addition to any critical damage the weapon supplies if it is a magic implement.