I tried following your advice, including manually rotating photos that were incorrectly rotated as part of the upload. I was able to insert into the post as a new gallery. However, I couldn't figure out how to make them work as a [slideshow]. Trying to add ids as with [gallery ids="2352,2353,2354,2355,2356,2357,2358,2359,2360,2361,2362,2363"] doesn't seem to work with [slideshow ids="2352,2353,2354,2355,2356,2357,2358,2359,2360,2361,2362,2363"]. I published the post with the photos as a gallery.
From my perspective, WordPress has removed capabilities that I used frequently, typically once a week with http://giftofmobility.wordpress.com/ and occasionally with other WordPress.com hosted sites. It is more than preference of work flow. I don't think it is possible to have [slideshow] work as long as the upload auto-rotates images incorrectly.