There have been a few discussions about self dimming mirror on our cars (or the lack thereof).
Anecdotally, I've found that the side mirrors do dim sufficiently given enough time when a light is directed at the sensor housed in the interior rear view mirror.
The issue is IMO, that the dimming process takes approximately 3x the duration as the interior rear view mirror. I think in most cases a driver would change lanes or adjust speed to reduce the glare irratant. This lends to the thought the side mirrors aren't dimming correctly.
Below is a short video I took of my side mirrors dimming. You'll note it takes about 3 times as much time to dim the side view mirrors. Also, notice how quickly the mirror returns to normal when the light source is taken away from the interior mirror sensor. Again a factor of 3.
So I wonder if there has been a physical hardware change between model years. I checked the coding and the coding has not changed between 2011 and 2012.