You should give Microsoft ICE a try on these images. ICE does almost everything automatically, but "leveling" doesn't always work out automatically. So, Microsoft ICE has a very good "orientation tool". This is a big advantage vs. rotating each of the input pics for several reasons. (1) obvious - you only need to set the rotation on the 1 output image vs all of the input images (2) less obvious - each pass of rotating an image will introduce a little more blur, the combination of rotating the input + doing the panorama projection will be slightly "softer" than letting ICE do this all in one step.