Hey! I was accepted into the entering class of 2012, and from what I read we seem to have very similar profiles. I also got a 330 on my OAT (some sections higher than others), my GPA was around the same, and I also had lots of experience job shadowing, working and volunteering for Optometrists over the years. So, I would say you have a good shot, the experience working for an O.D definitely counts for something! Not only does it show that you are knowledgeable about your career choice but also it will help you very much for the interview!
So from what I got out of my experiences applying to Waterloo and now being accepted is that experience is KEY, the more the better. GPA and OAT definitely count but as long as your in range and like you said not lower than 300 in any sections it shouldn't hinder you much it's just more a comparative against other applicants. I applied twice to the program, was accepted the second time, and my OAT score was the same, the improvements I made were in job experience (volunteering, job shadowing and working), GPA, and extracurriculars.
Hope this helps! This site was gold for me when I was applying so I am happy to give back!