There are several articles on T-Nation that address caring for the rotators (do a search), and other smaller back muscles. In all, developing balance in the shoulder girdle. If you have any imbalances, they could cause injury.
I've dislocated my right shoulder twice over the years, and I'm just now beginning to do the exercises linked in the above post. I'm not small, nor weak, but to give you an example of what can happen, two days ago, I did exercise #2 from the posted link. Two sets of 15 with no weight, and one set of 15 with 2.5lbs. (not a typo). My shoulder was extremely sore the entire next day, and it felt as if I had injured it. Today, it is perfectly fine, but those 3 little sets set it in fits. I obviously have a lot of rehab to do....
I highly recommend taking care of any imbalances in your shoulder girdle, once diagnosed. Perhaps, try the exercises, start very light, and see if they cause any pain or there is any perceived weakness in these small muscle groups.