how to separate taxonomy hierarchy in pathauto with slashes
There is a clever way to do this by using join:/

In my case, I used:

[node:field-taxonomy-skolski:parents:join:/]

where field-taxonomy-skolski is the field for choosing the term from the taxonomy tree.
Forward slashes will be stripped, though there is a setting under

Administration » Configuration » Search and metadata » URL aliases » URL aliases - settings

at the bottom of the page for PUNCTUATION drop-down. Set to slash (/) "no action" instead of "remove".