Yeah, I think it could be better. I had a lot of trouble getting it right, and it required hacking with OpenSeadragon a bit to adjust from the default easing, which was meant for applying to user-drag actions not automated pan-and-zoom, and was definitely inappropriate by default.
Do you have any suggestions as to what characterstics of the animation/easing are causing eye strain or what sorts of changes would result in better?
It's tricky to figure out good algorithms for moving from any arbitrary view to any other, with easing and timing etc. Sometimes the pan/zoom is just moving a little bit, in those cases zooming all the way out and back in again would be wrong. So you've got to take all of that into account with some good heuristics in an algorithm.
Tricky, but also kind of fun, I'll take another go at it sometime.