Hi,
eventually we did not go on with Totara + Oracle, we stayed for now on mysql but still are open for our clients that use Oracle.
We have done the same as you mentioned on Moodle 2.2 and 2.4, but not on Oracel 10g - on Oracle 11g. The clob data was the biggest problem. We also implemented php accelerator, which we did not have at the beginning, add extra ram onm server, excluded some options on moodle settings etc, there were some better results but still sites with mysql are much faster.
Regards
Tom