Hierarchical Taxonomy list pages
So i have similar issue, and i solve this by creating 2 views.
First view show taxonomy terms and i group them by theirs parents (add relationship Taxonomy term: Parent)
Second View is override on taxonomy/term/% and i add more Context (Arguments) for each level add an argument, and finally i add into header another view, who shows only children terms of current term.

You can view my work at http://www.attorney-directory.net/practice-areas