A user has created a document library with items about clients and
cases organized in several levels of folders. He has put a column on
the folders (3 levels deep) to indicate the type of case it is (Client
> Matter > Deal ... and on the deal folders there is a 'case type'
column).

It is easy to browse from the top, where you see the folders by
client, but is there a way to create a view that shows the data
grouped by the type of case, showing the folders? (i.e. show all tort
reform cases, then be able to select a client from there). I don't
want to have to tag every file with the client and case type.

I have tried a view that shows all files without folders, but the case
type metadata is actually on the folder, and doing this hides the folders.

I have looked a bit into using search to return items with the managed
property of 'case type' (the column with the metadata), but would this
be the best way? Is there a way to do it in the document library list
view?