I would send an IRIS. For me, I elected a DRO review when they ignored my treatment with immunosuppressive therapy for 5 years for psoriasis. From the time I gave them a NOD and asked for a DRO review, it took about 10 months for them to grant my appeal completely. However, I literally sent perhaps 15 IRIS inquiries, and from the amount of times that I got confused responses, I got the impression I would have waited at least 2 years in order to get it resolved without constantly quizzing them. You also may want to ask for a reconsideration instead of the whole DRO review, as I have heard this is faster.
When I finally got the Statement of case that granted my NOD, I was impressed with the thoroughness of the response. This was in the Phoenix VARO.
Hope this helps :-)