The relevant bug is MDL-25492 and the fix was integrated in the 2.3 stable branch with build 20120831 (yes that's just a few weeks after the build you are using, so it's quite normal import doesn't work in your Moodle because it was broken since Moodle 2.0).
I suggest you don't upgrade to 2.3.3 but to 2.3.3+ (or even better to 2.4+ if you can) so that you integrate even more bugfixes.
As the fix has been tested with numerous Examview files, I am very confident your files will import fine after your upgrade. If they don't this would show that either the file is defective or there is a bug in the code. If you are not able to import some of your files after upgrade, please report here so we can find what is wrong.