Are you sure all the seals/parts that are suppose to be in the mirror are installed? Possible that something got left off your car at the factory or the mirrors were incorrectly installed.

 

Good question. These are the parts that are there right now ...
Outside:
1. Exterior mirror unit
2. Rubber seal

Inside (door):
1. Plastic cover

Exterior mirror unit is held by 2 screws on the inside of the door. Lots of butyl gum is used to cover the edges from leaks. Since the new seals made it worse, I put some more butyl tape around the edges. A plastic piece covers it on the inside with 3 screws.
After reading your question, I am wondering if there should be any foam or sound deadening pads in place of butyl gum.

 

I bet that's it. Try some closed cell foam in that cavity, won't let wind or any sound through.

 

Did you ever get this figured out? I am having a similar issue with a 2012 Rapide. Wind noise seems to be coming in from the triangular section of glass closest to the driver door mirror.

 

Dealer fixed it .. no issues until recently. I noticed glass rocks a little bit and allows wind into the cabin. There seems to be a hair line gap between glass and frame .. glass needs to go all the way under the frame. Window reset won't help. Glass may have dropped down a little bit and needs adjustment ... getting this taken care of next week at the dealership.

 

If you're hearing wind noise from the glass you could replace the rubber seal around the window frame, or apply some carmex to soften it up and get it to seal properly again. That handy little trick served me well a couple decades ago; I owned a '98 Pontiac Trans Am with t-tops, which is notorious for rubber seals on the t-bar that harden and allow water and wind noise in. A little carmex fixed it right up.

I use it periodically on my window, hatch, and hood seals on the Vantage.

 

I regularly use Sonax or 303 or Gummi Pflege on all rubber seals. Replaced external mirror seals. Noise issue was fixed by dealer tech sometime back. Over time, glass seemed to have slipped a little bit and not going completely under the frame. This got nothing to do with doors rubber seals. Will post back after appointment.