Starting from Oracle 11gR2, exp is deprecated and will exclude empty tables from the dump file (not even the table definition). The fact that exp is deprecated does not make it less than a bug, especially when the proposed replacement expdp is a DBA-only tool that generates the dump files on the database server…
At least for this release, setting DEFERRED_SEGMENT_CREATION to false and issuing alter table T move; and alter index I rebuild; for all tables and indexes created previously seems to make exp to work a little better. For the next releases this may not work and there may not be any suitable workaround.
Oracle really needs to rethink expdp and make it work from a client installation only, the workaround that involves installing another Oracle DB of the exact same version and connecting the 2 databases via a DB link is nothing short of absurd.