Stump of time has hit rating. Priests have a glyph that provides smite with an 18% hit bonus, not requiring disc priests to have hit rating in order to smite heal.
Mandala of Stirring Patterns works for healing spells. Smite is not counted as thus, and such would not proc it.
The boost in spell power on the stump would be beneficial, but the hit rating would not. Just get glyph of divine accuracy and the mandala of stirring patterns.