MySQL Host 'host_name' is blocked - Which Database?
I am not sure that you can get the database, but you can identify the user with one of the following methods:


The general log
The error log (log_warnings = 2)
An extra patch called user statistics (included by default in Percona and MariaDB)
An audit plugin like McAfee's


The first three are mentioned on this article on MySQL performance blog.

Sadly, visilibity on the host cache was only added until 5.6 on performance_schema.host_cache. 

As a temporary workaround, you would be required to set max_connect_errors to a large value instead of 10, and set MAX_CONNECTIONS_PER_HOUR and MAX_USER_CONNECTIONS per user to an appropriate value (you should be using different users if you are not, and/or different DNS names).