I agree that a good SD can make all the difference for the quality of a flight. They set the tone for the rest of the crew.
One idea to address the inconsistent service would be to establish a simple website where we could post our experiences. Alternatively, just create a dedicated thread for this on Flyer Talk.

Rate your Air Canada Service Director

Date - Orig - Dest - Flt No - SD 1st Name - Rating 1 to 5 - Comments

2014/03/28 .... YVR - HKG 007 ..... John .... 5 .... Excellent service