I booked this flight for the first week of March. When I was booking it QR web site indicated equipment A351. Then it switched to A330. I called QR to assign seats and they pulled up a seat map where business class is 2-2-2 four rows 10-14. Turned out that this flight is operated by Oman Air A330-300V1 - two class configuration. This is confirmed by expert flyer. My reservation on Qatar says flight operated by Oman Air flight number WY663.
Hope this helps. Call Qatar for seat assignments. I was bale to do my seat assignment online on Sri Lankan web site as the fist segment of my itinerary is MLE-CMB operated by Sri Lankan Airlines. Their web site allowed me to assign seats on Sri Lankan, Qatar operated by Oman, and another Qatar flight to Europe.