Let's do a quick prototype of a slider that appears on diff pages, showing the 50 most recent revisions.
When the user is trying to find particular edits within the last 50 revisions, the slider will help the user navigate through diff pages without having to go back and forth between the diff and history pages. This will save time and page loads.
On the diff page, when the two revisions that you're viewing are both within the 50 most recent revisions:
A horizontal slider appears above the two revision columns.
The slider has 50 notches to represent the most recent 50 revisions.
There are two "knobs" on the slider, representing the revisions that you're currently comparing.
There is a small popup label that appears above each knob. The label displays the user name and the timestamp of the corresponding revision.
(I think this will probably be seen on hover over the knob -- if both labels are open all the time, then they'll run into each other when the knobs are too close. But it's an open question, if you can think of something smart.)
When the user moves one of the knobs, the label changes, showing the name and timestamp of that position on that slider.
The diff itself does not change when the user moves the knobs.
There is a button at the right end of the slider that says "Go". When the user clicks that button, the page reloads, showing the diff of the two revisions represented by the knobs.
If the user loads a diff that is outside of the most recent 50, then the slider doesn't appear.