Interesting to see the responses here. I'm also retaking with 22AA and 20PAT. My PAT was fairly low for the school I am applying to (UBC) and people with 1 score higher on the PAT (with same GPA as me) received an interview whereas I did not, so that is my reason for retaking. I don't see it too much as a waste of time, it's mostly review and polishing up the areas where you're weak-- and less costly then spending another year of undergrad with $400 per course to boost your GPA. But Canadian schools are a bit different since they only care about your numbers pre-interview (don't ask for EC's, recs) so I do think the responses here probably resonate some truth, but I still wouldn't go far as to say it's a complete waste of time.