Things were working great until I realized that my queries were truncating strings that were too large in a given element. The datatype is set to LONG on the ORACLE server.
I've searched around a bit and found a few other references about this happening to people but have found no working solutions. I tried upgrading the MDAC to the latest revision, 2.8, as well as the ORACLE ODBC driver to 18.104.22.168.9.
Most commonly the solutions included a reference to the switch titled "Force Retrieval of Longs" in the ORACLE ODBC driver, stating that turning this switch on would correct the problem. In fact I had to enable that switch to read back the smallest of my data and now some are exceeding an apparent limit of ~100k (97.6K to be exact) as they are all truncated to that size.
Solved the problem. I tried logging in under a different username and was able to retrieve all the data. There are multiple sets of the same tables and apparently the server-side scripting was incorrectly populating some of the tables and setting the LONG size limit to 100k.