> I don't want to just see the final state of ours/theirs, but the changes that us/them did in order to get to those final states.

I'm curious, would something like this help you better understand a complex merge?

https://public.gitsense.com/insight/github?r=Microsoft/vscod...

If you click on the files in the pull request, you can see the diff and the changes on the source and target branches at once. You can also search for diffs on both branches at once, to quickly see how they were introduced.

Disclaimer: I'm the creator behind GitSense