Tried that, that works fine. Apache mod / DLL and test program 64Bit, Delphi XE6 DOA 4.1.3.5, Apache/OHS is running as local system account, the exe with my local administrator account.
"Forcing" a different OCI dll works with the test executable as well. Does not work with OHS, guess the OCI layer is loaded before the Apache module is initialized. Both homes contain the same version of Oracle.