First of all with just the inclusion of taxonomy I wasn't able to get the desired URL, let alone the hierarchical representation. For that include the pathauto module and include the pattern as blog/[termpath-raw]/[dd]/[mm]/[yyyy]/[title-raw] in the pattern for all blog entry paths of the node path settings in automatted alias settin.

To delete all the url aliases generated automatically as well as user created go to

site building -> URL alias -> delete alias

when doing this be careful that the opening page/home page may misbehave due to user defined url not being found.

To generate bulk url using autopath go to

site building -> URL alias -> automatted alias setting and check the bulk generate aliases for nodes that are not aliased in the node path settings.

IMP:- Have the drop down list of the blog class by unchecking the tag in the add vocabulary section of the taxonomy.