You're accessing data in very different ways when comparing SQL Developer and SSRS so that comparison really doesn't matter.
Are you using the built in provider, extension for Oracle? If so, please refer to the documentation where it says:
The data processing extension OLE DB for Oracle does not support the following Oracle data types: BLOB, CLOB, NCLOB, BFILE, UROWID.
The documentation can be found here:
Data Sources Supported by Reporting Services
Sue