Remember the dot wrote:
What do you think? Should we keep the redundant tooltips, or start leaving them out?
I'm in the camp that considers them redundant. If the title isn't adding anything that isn't already visible, it's not helping.
One suggestion that hasn't been mentioned is leaving these as titles in interactive settings (tooltip in web page) and using CSS to generate inline text in others (caption when printed). Online, images that have a tooltip could be distinguished from those that don't by some subtle effect, like maybe a thin border.
Tim