I was charged with a DUI in Oregon and completed a diversion court-ordered program, consequently the charge was dismissed after a year without a conviction. I researched the subject-matter, and under Oregon law a DUII diversion cannot be expunged.
Unfortunately, you are correct. Oregon law does not permit a DUII arrest to be removed from your record, even if you successfully complete Diversion. The only way the arrest can be removed is if you go to trial and win, or if the case is dismissed for a reason other than Diversion.
One important thing to also keep in mind is that even though the diversion is on your record. When filing out information (housing, jobs, etc...) and they ask if you have been convicted of a crime, the answer is NO. Unless there is something else on your record.
Your criminal record will always show that you were charged with DUI and that you "went diversion." The suggestion by the courts and the prosecutors that this charge will "go away" after a year is misleading, at best. The charge, your guilty plea, your entry into diversion -- these stay on your record forever. Diversion is not Generally, the only reason for entering diversion is to avoid a license suspension and save a few hundred dollars.