Blizzard has various teams including system engineering and game engineering that works at all levels of the game. Furthermore, Blizzard is hiring many positions as they are expanding and continuing to develop Overwatch:
I maintain a Dev Post directory which has a listing of answers from developers on why many features are or are not included. Please note, many of the posts from devs were on the older forum platform which is no longer accessible, but you will find the general summary of those responses in this thread.