What's the probability of a 0, 7, 3 distribution if each spell is equally distributed?

We can group the two non-rotting flesh spells together, which means that there is a (2/3)^10 (approximately 0.0173) probability of only non-rotting flesh spells or roughly a 2% chance of this happening, which is a low probability event, but not completely ridiculously low.

Eg. I would not be at all surprised if you can just chalk this up to an infrequent and unlikely event rather than a bug in the load rate.