I would recommend sealing around any holes in the bracket and it's not a bad idea to use foam tape to seal the bracket to the door. Duct tape would be better than nothing, however something firmer would be better, self adhesive sound deadening material, even blue tack and duct tape. The bracket should also be very rigid, and seal around the wires if they also pass through the bracket, I just use hot glue for this. Pull the wire 1/4" in, apply hot glue around the hole/wire and pull the wire back the 1/4" so it pulls the glue into the hole and seals better. The same process works well with silicone, caulk etc.