That query can take several different forms depending on privileges and which schema (logon schema vs. another schema) you are querying against.
Those ALL_ views can be slow, and the do take oracle privileges into consideration, so it's certainly a possibility that your recent security changes had something do to with it.
If you are looking in your own schema, Toad will use the USER_ views as much as possible, and those are a lot faster than ALL_.
If you grant select on DBA_SOURCE, DBA_OBJECTS, DBA_PROCEDURES to your user then you should see some improvement.
Taking it further, if you have select on SYS.IDL_CHAR$, SYS.PROCEDUREINFO$, SYS.USER$, and SYS._CURRENT_EDITION_OBJ (11g or newer) or SYS.OBJ$ (10gR2 or older), then the query will use these tables instead of the USER/ALL/DBA views and will be much faster.
Toad only checks for privileges on these views when you first make a connection, so be sure to disconnect and reconnect after making them. And make sure that Options->Startup->"Check for access to DBA Views" is checked.